The nature of the protein moieties of cartilage proteoglycans of pig and ox.

Proteoglycans extracted with 4M-guanidinium chloride from pig laryngeal cartilage and bovine nasal septum were purified by density-gradient centrifugation in CsCl under 'associative' followed by 'dissociative' conditions [Hascall & Sajdera (1969) J. Biol. Chem. 244, 2384-2396]. Proteoglycans were then digested exhaustively with testicular hyaluronidase, which removed about 80% of the chondroitin sulphate. The hyaluronidase was purified until no proteolytic activity was detectable under the conditions used for digestion. The resulting 'core' proteins of both species were fractionated by a sequence of gel-chromatographic procedures which gave four major fractions of decreasing hydrodynamic size. Those that on electrophoresis penetrated 5.6% (w/v) polyacrylamide gels migrated as discrete bands whose mobility increased with decreasing hydrodynamic size. The unfractionated 'core' proteins had the same N-terminal amino acids as the intact proteoglycan, suggesting that no peptide bonds had been cleaved during hyaluronidase digestion. Alanine predominated as the N-terminal residue in all the fractions of both species. Fractions were analysed for amino acid, amino sugar, uronic acid and neutral sugar compositions. In pig 'core' proteins, the glutamic acid content increased significantly with hydrodynamic size, but in bovine 'core' proteins this trend was less marked. Significant differences in amino acid composition between fractions suggested that in each species there was more than one variety of proteoglycan. The molar proportions of xylose to serine destroyed on alkaline beta-elimination were equivalent in most fractions, indicating that the serine residues destroyed were attached to the terminal xylose of chondroitin sulphate chains. The ratio of serine residues to threonine residues destroyed on beta-elimination, was similar in all fractions of both species. Since the fractions of smallest hydrodynamic size contained less keratan sulphate than those of larger size, it implies that in the former the keratan sulphate chains were shorter than in the latter.     

A convenient plate assay for the quantitation of hyaluronidase in hymenoptera venoms

A simple plate assay for hyaluronidase activity in biological samples is described. Hyaluronic acid is incorporated into agarose gels and the enzyme is allowed to diffuse from punched wells. The undigested hyaluronic acid is then precipitated with cetylpyridinium chloride and the diameters of the clear circles are proportional to the logarithm of the enzyme concentration applied to the well. The assay was utilized to examine commercially available hymenoptera venoms, manufactured for use in allergy diagnosis and treatment, for their content of hyaluronidase as a measure of lot-to-lot consistency. The assay permits the analyses of a large number of samples with good reproducibility, without the need for any special instrumentation. Based on the quantity of purified hyaluronidase reported in honey bee venom (T. P. King, A. K. Sobotka, L. Kochoumian, and L. M. Lichtenstein, 1976, Arch. Biochem. Biophys.172, 661–671) we estimate that the assay should detect 70 ng/ml of purified honey bee venom hyaluronidase.     

Interfacial behaviour of bovine testis hyaluronidase

The interfacial properties of bovine testicular hyaluronidase were investigated by demonstrating the association of hyaluronidase activity with membranes prepared from bovine testis. Protein adsorption to the air/water interface was investigated using surface pressure-area isotherms. In whichever way the interfacial films were obtained (protein injection or deposition), the hyaluronidase exhibited a significant affinity for the air/water interface. The isotherm obtained 180 min after protein injection into a pH 5.3 subphase was similar to the isotherm obtained after spreading the same amount of protein onto the same subphase, indicating that bovine testicular hyaluronidase molecules adopted a similar arrangement and/or conformation at the interface. Increasing the subphase pH from 5.3 to 8 resulted in changes of the protein isotherms. These modifications, which could correspond to the small pH-induced conformational changes observed by Fourier-transform IR spectroscopy, were discussed in relation to the pH influence on the hyaluronidase activity. Adding hyaluronic acid, the enzyme substrate, to the subphase tested the stability of the interfacial properties of hyaluronidase. The presence of hyaluronic acid in the subphase did not modify the protein adsorption and allowed substrate binding to a preformed film of hyaluronidase at pH 5.3, the optimal pH for the enzyme activity. Such effects of hyaluronic acid were not observed when the subphase was constituted of pure water, a medium where the enzyme activity was negligible. These influences of hyaluronic acid were discussed in relation to the modelled structure of bovine testis hyaluronidase where a hydrophobic region was proposed to be opposite of the catalytic site.     

Localization of hyaluronic acid in synovial cells by radioautography

Cultured human synovial cells secrete hyaluronic acid (HA) into the culture medium. Glucosamine-6-³H was shown to be a direct and relatively specific precursor of HA-³H by the following observations: the susceptibility of nondialyzable radioactivity in the medium to hyaluronidase, its migration with hexuronic acid on zone electrophoresis in polyvinyl chloride, its exclusion from Sephadex G-200, and the localization of radioactivity to glucosamine after hydrolysis of the labeled polysaccharide. The presence of intracellular HA-³H was established by sequential extraction of labeled cells and by radioautography of synovial cell cultures digested with hyaluronidase in situ. When cells were exposed to medium lacking glucose, glucosamine-³H-uptake was enhanced; and this made possible electron microscopic radioautographic studies. These studies demonstrate the early and continued presence of HA-³H within the Golgi apparatus.     

Effects of hyaluronidase, trypsin, and EDTA on surface composition and topography during detachment of cells in culture

Cultured human embryo fibroblasts (HLM18) were labeled with [3H]glucosamine and Na35SO4, and then treated with testicular hyaluronidase, trypsin, or EDTA. Macromolecular material from the surface of these cells was characterized by DEAE-cellulose chromatography and cetylpyridinium chloride precipitation while the associated morphology of cell detachment was studied by phase contrast and scanning electron microscopy. Release of surface glycosaminoglycans by testicular hyaluronidase did not cause cell rounding or detachment. EDTA did not release cell-surface components, but caused cell contraction and detachment morphologically similar to that caused by trypsin. Large amounts of cell-surface glycoproteins and glycosaminoglycans were released by trypsin. From these observations it is concluded that hyaluronic acid is not a principal adhesive agent in the attachment of cells to a substrate. It is suggested that both EDTA and trypsin may have their primary effect upon the cytoskeleton.     

Hyaluronic acid-degrading enzymes in rat alveolar macrophages and in alveolar fluid: stimulation of enzyme activity after oral treatment with the immunomodulator RU 41740

RU 41740 (Biostim) is an immunomodulator clinically used for the treatment of chronic bronchitis and recurrent pulmonary infections. In these diseases large amounts of mucus are produced which congest the bronchi. A major glycosaminoglycan constituent of this mucus is hyaluronic acid, one of the largest molecules in nature; its metabolic degradation is carried out by 3 acid hydrolases: hyaluronidase, beta-N-acetylglucosaminidase, and beta-glucuronidase. In the lung these enzymes are especially synthesized and active in alveolar macrophages. It was thus interesting to study the effect of RU 41740 administration on the hyaluronic acid-degrading activity of these cells. This compound was given by gastric gavage to rats and the activities of lung alveolar macrophage and alveolar fluid hyaluronidase, beta-N-acetylglucosaminidase, beta-glucuronidase, and acid phosphatase as a lysosomal marker were determined. The effect on macrophage proliferation was also examined. The results obtained showed that: (1) unstimulated alveolar macrophages display the remarkable property, compared with other cell types, that hyaluronidase activity is about equally distributed between the inside and the outside of the cell; (2) RU 41740 administration increases the total activity of the 4 enzymes studied in the alveolar macrophages without inducing any increase in the number of macrophages; (3) the intracellular activities of beta-N-acetylglucosaminidase and beta-glucuronidase are markedly increased, whereas intracellular hyaluronidase activity is not changed. However, in the extracellular fluid only hyaluronidase activity is highly increased; (4) even the lysosomal marker enzyme acid phosphatase has only its intracellular activity increased. This would suggest the possibility that other lysosomal enzymes may also be increased by this immunomodulator.(ABSTRACT TRUNCATED AT 250 WORDS)     

Further evidence for hyaluronidase activity of Treponema pallidum

The presence of hyaluronidase in preparations of Treponema pallidum was previously shown using acidified bovine serum albumin reactions and Ouchterlony immunodiffusion. To expand on these preliminary findings more sensitive techniques of viscometry, additional immunologic reactions, and altered capillary permeability were used to characterize treponemal-associated hyaluronidase. The pathogens T. pallidum and T. pertenue degraded hyaluronic acid, whereas the nonpathogens T. denticola and T. vincentii did not. As syphilitic infection progressed, hyaluronidase activity decreased; organisms harvested from 14-day testicular infections degraded hyaluronic acid less rapidly than organisms from 4-day infections. Uninfected rabbit testicular extract also exhibited significant enzyme activity. The neutralizing activity of immune sera was decreased by prior adsorption with bovine hyaluronidase, suggesting that some of the neutralizing factors are associated with this enzyme. Radioimmunoassay was used to quantitate antibodies to hyaluronidase in immune sera. Antihyaluronidase sera were isolated from rabbits immunized with bovine hyaluronidase. Treponema pallidum, as well as uninfected rabbit testicular extract, cross-reacted with these antisera. Immunofluorescence indicated that the hyaluronidase was uniformly distributed along the treponemal surface. As a final indicator of hyaluronidase activity, alterations in capillary permeability were detected 1 h after intradermal injection of T. pallidum.     

Canine submandibular-gland hyaluronidase. Purification and properties

1. Methods for the purification of dog submandibular-gland hyaluronidase from sedimentable and non-sedimentable portions of a homogenate and from the whole homogenate are presented. The method consists of three main steps: removal of mucin by acid precipitation or gel filtration on Sephadex G-200, ammonium sulphate precipitation and CM-cellulose chromatography. By this method specific activities of up to 1.28 and 0.78mumoles of N-acetylglucosamine/min./mg. of protein were obtained for the purified freeze-dried non-sedimentable hyaluronidase and for the sedimentable hyaluronidase respectively. 2. A comparison of some of the properties of the non-sedimentable and the sedimentable hyaluronidase preparation indicated that there was little difference between the two and that they both resembled lysosomal hyaluronidase from rat liver.     

Effect of hyaluronidase, beta-glucuronidase and beta-N-acetylglucosaminidase inhibitors on sperm penetration of the mouse oocyte

The role of hyaluronidase, beta-glucuronidase and beta-N-acetylglucosaminidase in the penetration by mouse spermatozoa through the layers surrounding the oocyte was investigated by in vitro techniques. Myocrisin, fenoprofen, phosphorulated hesperidin and PS53 (a hydroquinone-sulfonic acid-formaldehyde polymer) inhibited fertilization when incubated with capacitated spermatozoa before the treated spermatozoa were mixed with intact oocytes but not when the inhibitor-treated, capacitated spermatozoa were added to oocytes free of follicle cells. The antifertility activity did not appear to be due to an effect on sperm motility or on the oocytes. These 4 compounds are known hyaluronidase inhibitors and, of the acrosomal enzymes tested, only share inhibition of hyaluronidase. Kinetic studies indicated that myocrisin is a reversible inhibitor of mouse sperm hyaluronidase whereas the other three are irreversible inhibitors. Adding saccharolactone, a beta-glucuronidase inhibitor, or N-acetylglucosaminolactone and N-acetylgalactosaminolactone, beta-N-acetylglucosaminidase inhibitors, to capacitated spermatozoa under the same conditions as the hyaluronidase inhibitors did not decrease fertilization. This was the case even though the beta-glucuronidase or beta-N-acetylglucosaminidase activities of the spermatozoa were completely inhibited, at least at the time that the inhibitor-treated, capacitated spermatozoa were mixed with the oocytes. The hyaluronidase activity of mouse spermatozoa remained unaltered during the incubation period required for capacitation; however, prolonged incubation caused a significant decrease in hyaluronidase. Untreated mouse spermatozoa caused hydrolysis of hyaluronic acid more effectively than did sperm extracts obtained by detergent extraction. These results are consistent with the theory of an essential role of hyaluronidase in mouse fertilization. At least in this species, the enzyme appears to be specifically involved in sperm penetration through the follicle cell layer. The data do not support an essential role for beta-glucuronidase and beta-N-acetylglucosaminidase in the penetration by mouse spermatozoa through the oocyte's investments. In contrast to some other species, sperm capacitation in mice does not result in a loss of hyaluronidase although part of the enzyme activity is lost on prolonged incubation. Mouse spermatozoa appear to be able to digest substrate (hyaluronic acid) even though hyaluronidase is not released.     

Quantitative determination of hyaluronidase in tissue sections

Summary A method for the determination of hyaluronidase in histological sections is described. This method is based on incubation of tissue sections in a medium containing hyaluronic acid as substrate. Depolymerisation of the substrate during incubation as well as the total nitrogen content are measured in the same section. The comparison of these two values gives information concerning the hyaluronidase activity. This assay was tested in experiments with rat testis. It was also found that our procedure is sensitive enough for the estimation of hyaluronidase activity in sections from kidney. From these experiments with kidney sections it can be concluded that: 1. The pH optimum for renal hyaluronidase (3.5) differs from that in the testis (4.7). 2. In the renal cortex more hyaluronidase activity was detected than in the medulla.Department of Transplantology.Department of Histology and Embryology.     

Hyaluronidase dissolves a component in the hamster zona pellucida

Mammalian sperm must pass between cumulus cells and corona radiata cells before reaching the surface of the zona pellucida which surrounds the oocyte. The cumulus and corona radiata cells are separated from each other by an extracellular matrix (ECM) containing hyaluronic acid. The structure of this ECM and of the zona pellucida was investigated in the hamster oocyte-cumulus complex (OCC) using transmission electron microscopy (TEM) following processing in ruthenium red. When fixed in the presence of ruthenium red, the ECM of the OCC and the zona pellucida were well preserved and highly structured. The ECM between corona radiata cells was comprised of a network of granules and filaments which resembled hyaluronic acid containing matrices described in other systems. The outer one-third to one-half of the zona pellucida was porous; the ECM of the corona radiata extended into these pores. Bovine testicular hyaluronidase, Streptomyces hyaluronidase, and hamster sperm extracts containing hyaluronidase each dispersed the cumulus cells and most of the corona radiata cells. TEM examination revealed that brief (5-10 min) hyaluronidase treatment of OCCs removed the matrix filaments and caused clumping of the granules in both the corona radiata and zona pellucida. Longer hyaluronidase treatments (15-30 min) removed both filaments and granules. Our observations are consistent with the ideas that: 1) the ECM between corona radiata cells contains hyaluronic acid, and 2) hyaluronic acid is present in the outer one-third to one-half of the zona pellucida.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improved Yield of High Molecular Weight Hyaluronic Acid Production in a Stable Strain of <Emphasis Type="Italic">Streptococcus zooepidemicus</Emphasis> via the Elimination of the Hyaluronidase-Encoding Gene

Despite the significant potential of Streptococcus zooepidemicus for hyaluronic acid (HA) production with high molecular weight (MW), the HA degrading properties of hyaluronidase prevents the bacteria to achieve enhanced HA yield with high MW. In the present study, we aim to knockout the hyaluronidase enzyme and assess its effects on the yield and MW of the produced HA. The kanamycin resistance gene between the left and right arms of hyaluronidase gene was inserted into pUC18 plasmid to construct pUC18-L-kana^r-R as a recombinant suicide plasmid. The construct was then transferred into S. zooepidemicus to induce the homologous recombination between the hyaluronidase gene and the kanamycin resistance gene. Gene deletion was confirmed by PCR and enzyme assay. The product was cultured on selectable medium in which the MW of HA was increased from 1.5 to 3.8 MDa. The yield of HA production using the mutant strain was higher in all different concentrations of glucose from 40 to 120 g/l. Moreover, glucose increase results in higher HA production within both wild-type and recombinant strains. However, the growth rate of HA concentration (the slope of the plot), as a consequence of increased glucose concentration, is always higher for the recombinant strain. Unlike the wild-type strain, there was no sharp HA production drop approaching the 6 g/l HA concentration. In conclusion, hyaluronidase activity and HA concentration and MW exhibited a mutual control on each other. Based on our results, deletion of the hyaluronidase gene positively affects the yield and MW of HA.     

Attempted isolation of a heparin proteoglycan from bovine liver capsule

(1) Polysaccharides were isolated from bovine liver capsule by extraction with 2m-potassium chloride followed by precipitation from 0.8m-potassium chloride with cetylpyridinium chloride. Chondroitin sulphate was eliminated by digestion with hyaluronidase. The yield of heparin was approx. 40% of that obtained after extraction of the papain-digested tissue. (2) The macromolecular properties of the hyaluronidase-digested polysaccharide were studied by gel chromatography on Sephadex G-200 of the intact, as well as of the alkali-degraded, material. The results suggested the presence of single heparin chains in addition to a dermatan sulphate proteoglycan. (3) A purified heparin preparation was analysed for amino acids and neutral sugars. Xylose, galactose and serine were found in amounts corresponding to 0.1, 0.2, and 0.4 residue/polysaccharide chain (mol.wt. 7400), respectively. It is suggested that the isolated material had been degraded by a polysaccharidase with endo-enzyme properties.     

Inhibition of Naja naja venom hyaluronidase: role in the management of poisonous bite

Hyaluronidase is present virtually in all snake venoms and has been known as a "spreading factor." The enzyme damages the extracellular matrix at the site of the bite, leading to severe morbidity. In this study, the benefits of inhibiting the hyaluronidase activity of Indian cobra (Naja naja) venom have been investigated. Anti-NNH1 and aristolochic acid both inhibited the in vitro activity of the purified hyaluronidase, (NNH1) and the hyaluronidase activity of whole venom in a dose-dependent manner. Both anti-NNH1 and aristolochic acid abolished the degradation of hyaluronan in human skin tissue sections by NNH1 and by whole venom. Aristolochic acid quenched the fluorescent emission of NNH1. A non-competitive mechanism of NNH1 inhibition was observed with aristolochic acid. NNH1 potentiates the toxicity of Daboia russellii VRV-PL-VIII myotoxin and hemorrhagic complex-I. However, the potentiation of toxicity was inhibited dose-dependently by anti-NNH1 and aristolochic acid. Further, mice injected with whole venom which had been preincubated with anti-NNH1/aristolochic acid, showed more than a two-fold increase in survival time, compared to mice injected with venom alone. A more moderate increase in survival time was observed when mice were injected with anti-NNH1/aristolochic acid 10 min after whole venom injection. This study illustrates the significance of venom hyaluronidase in the pathophysiology of snake venom poisoning and the therapeutic value of its inhibition.     

The major human urinary trypsin inhibitor is a proteoglycan

The major urinary trypsin inhibitor (Mr 44 000), isolated from human urine, contains 35% carbohydrate. In addition to N-acetylglucosamine and neutral sugars (primarily mannose and galactose), the carbohydrate moiety contains hexuronic acid and N-acetylgalactosamine and corresponds to a glycosaminoglycan. This carbohydrate chain is an integral component of the inhibitor: it does not dissociate from the inhibitor when using dissociative conditions such as sodium dodecyl sulfate, guanidinium chloride, or by increasing ionic strength or mixing with cetylpyridinium chloride. This glycosaminoglycan chain is sensitive to chondroitinase ABC or testicular hyaluronidase digestion and corresponds to slightly sulfated chondroitin 4-sulfate or 6-sulfate. After treatment by these enzymes, the urinary inhibitor has a lower molecular mass (Mr 26 000) but still inhibits trypsin.     

Role of the glycosaminoglycan microenvironment of hyaluronidase in regulation of its endoglycosidase activity

The glycosaminoglycan microenvironment of testicular hyaluronidase was simulated by multipoint covalent attachment of the enzyme to glycans as a result of benzoquinone activation. The efficiency of their binding was assessed using gel chromatography, ultrafiltration, titration of surface amino groups of the enzyme, electrophoresis, as well as judging by the value of residual endoglycosidase activity and its inhibition with heparin. Copolymer glycosaminoglycans, such as dermatan sulfate and heparin, inactivated the endoglycosidase activity as a result the C-5 epimerization of hexuronic acid. It was shown that glucuronic acid and, to a lesser extent, N-acetylglucosamine determine the specificity of hyaluronidase. The chondroitin-sulfate microenvironment made the enzyme resistant to heparin inhibition because the equatorial orientation of the OH groups is similar to that in hyaluronic acid. Model experiments with dextran and dextran sulfate showed that sulfation of the glycan chain increased its rigidity, thus hampering the stabilizing effect on hyaluronidase. The effect of chondroitin sulfate on the endoglycosidase activity of hyaluronidase had additive character and did not directly affect the small fragment of the active site of the enzyme located at the bottom of a groove. The glycosaminoglycan microenvironment of hyaluronidase, containing an iduronic acid residue, the 1-3 and 1-4 glycosidic bond, inactivated the hyaluronidase activity of the enzyme, whereas simple polymers (such as gluco- and galactoaminoglycans) potentiated it due to a similar way of linking—(1e-4e) and (1e-3e). To understand the nature of these interactions in detail, the effect of oligomeric glycosaminoglycan fragments and their derivatives on hyaluronidase should be studied.     

Purification and partial characterization of a novel hyaluronic acid-degrading enzyme from Antarctic krill (Euphausia superba)

Summary A novel enzyme degrading hyaluronic acid has been isolated, purified and characterized from Antarctic krill (Euphausia superba). A combination of affinity chromatography (Con A-Sepharose), gel filtration (Superose 6) and fast protein liquid chromatography (Mono Q) was used for the purification. The hyaluronidase activity was determined by a radial diffusion method based on hyaluronic acid incorporated into an agarose gel. Moreover, the beta-glucuronidase and endo-(1,3)-beta-D-glucanase activities were also followed through the process using phenolphtalein mono beta-glucuronic acid and laminarin as substrates. After the final purification step on Mono Q column, the chromatogram showed three main peaks designated A, B and C. Peak C contained high hyaluronidase activity undetectable in peak A and B. The betaglucuronidase activity was associated with peak A, while the endo-(1,3)-beta-D-glucanase activity was found in peak B and slight in peak C. The hyaluronidase was purified about 85-fold. It had a pH optimum of 5.3, a temperature optimum of 37°C and a molecular weight of 80 000 Daltons. On polyacrylamide gradient gel electrophoresis the enzyme fraction showed one major band associated with hyaluronic acid decomposition, slightly contaminated with a few other components. Isoelectric focusing in combination with a hyaluronic acid zymogram demonstrated one major band at pH 6.7 with high enzyme activity. Preliminary data on enzyme specificity suggest that krill hyaluronidase is a new endo-beta-glucuronidase and support the concept of krill enzymes as a remarkable and unusually effective digestive system adapted to the Antarctic marine ecosystem.     

Inhibitory effect of a hot water extract of coffee "silverskin" on hyaluronidase

Coffee "silverskin" (CS) is a by-product of the roasting procedure for coffee beans. A CS extract (CS-ext) was found to have a high inhibitory effect against hyaluronidase. It seems that the higher-molecular-weight substances in CS-ext contributed most to the hyaluronidase inhibition, while acidic polysaccharides mainly composed of uronic acid played a major role in this hyaluronidase inhibition by CS-ext.     

Recombinant human hyaluronidase Hyal-1: insect cells versus Escherichia coli as expression system and identification of low molecular weight inhibitors

The human hyaluronidase Hyal-1, one of six human hyaluronidase subtypes, preferentially degrades hyaluronic acid present in the extracellular matrix of somatic tissues. Modulations of Hyal-1 expression have been observed in a number of malignant tumors. However, its role in disease progression is discussed controversially due to limited information on enzyme properties as well as the lack of specific inhibitors. Therefore, we expressed human Hyal-1 in a prokaryotic and in an insect cell system to produce larger amounts of the purified enzyme. In Escherichia coli, Hyal-1 formed inclusion bodies and was refolded in vitro after purification by metal ion affinity chromatography. However, the enzyme was produced with extremely low folding yields (0.5%) and exhibited a low specific activity (0.1 U/mg). Alternatively, Hyal-1 was secreted into the medium of stably transfected Drosophila Schneider-2 (DS-2) cells. After several purification steps, highly pure enzyme with a specific activity of 8.6 U/mg (consistent with the reported activity of human Hyal-1 from plasma) was obtained. Both Hyal-1 enzymes showed pH profiles similar to the hyaluronidase of human plasma with an activity maximum at pH 3.5-4.0. Deglycosylation of Hyal-1, expressed in DS-2 cells, resulted in a decrease in the enzymatic activity determined by a colorimetric hyaluronidase activity assay. Purified Hyal-1 from DS-2 cells was used for the investigation of the inhibitory activity of new ascorbic acid derivatives. Within this series, l-ascorbic acid tridecanoate was identified as the most potent inhibitor with an IC(50) of 50 +/- 4 microM comparable with glycyrrhizic acid.     

Proteases from actinomycetes interfere in solid media plate assays of hyaluronidase activity

Four hundred and fifteen actinomycete strains were screened for hyaluronidase activity in two plate assays media. In the first one, using hyaluronic acid as substrate and bovine serum albumin (BSA) to help precipitation of the nondegraded substrate, only strain 594 and hyaluronidase control were positive. In the second assay, plates with hyaluronic acid, but not BSA, gave the same results. For plates containing only BSA, proteinase activity was detected in strain 594. When hyaluronic acid was treated with pronase, the only clear zones, in the second assay without BSA, were those around hyaluronidase controls. Protease activity, commonly found in actinomycetes, was detected only in strain 594, among the 415 studied, when tested in hyaluronidase assay using hyaluronate plus BSA. This may be due to the composition of the growth medium, since media with different composition gave different results for protease activity in each of the 15 strains analyzed. These data suggest that proteases can affect an accurate detection of hyaluronidase in media containing proteins, not only from hyaluronate preparations, but also from other medium ingredients. Thus, for a correct interpretation of the method, they must be excluded. Commercial Hyaluronidase used as controls must be also tested for the presence of protease contamination.