A note on hydrolytic enzymes of Corynebacterium equi

One hundred and five strains of Corynebacterium equi from various sources were examined for the production of 11 extracellular enzymes. Only lipase and phosphatase activity were detected in all strains. A small number of strains produced deoxyribonuclease but these strains were not confined to any one source. It seems likely that C. equi does not rely on a powerful array of extracellular enzymes to induce pathology.     

The capsules of Corynebacterium equi and Streptococcus equi.

The capsules of Corynebacterium equi and Streptococcus equi were examined by electron microscopy after staining with ruthenium red. They were compared with the capsule of Klebsiella pneumoniae which had previously been examined using the same procedure (Springer & Roth, 1973). The capsule of C. equi had a laminated appearance. When S. equi was grown on solid medium, its capsule appeared as radially arranged projections capped by a thick electron dense layer. When grown in liquid medium, S. equi produced a capsule which showed as short thick projections with no layer external to them.     

A convenient assay for siderochrome hydrolytic enzymes

Conditions are described under which ethylenediaminetetraacetate (EDTA) rapidly dissociates ferric ion from chelation with monohydroxamic acids and dihydroxamic acids, but under which the metal is not dissociated from natural trihydroxamic acids (siderochromes). Based upon this observation, enzymes which hydrolyze siderochromes to monohydroxamic acid subunits can be conveniently assayed spectrophotometrically. The characteristic absorption at 425–440 nm of the siderochrome decreases linearly during hydrolysis. The application of this assay to an enzyme isolated from an unidentified species of penicillium is described.     

Effects of hydrolytic enzymes on tomato protoplasts

Summary Living protoplasts were isolated from the interplacental tissue ofLycopersicum esculentum L. var.Manalucie with 5% polygalacturonase in 0.4 M sucrose solution. The protoplasts were treated under standardized conditions with eleven hydrolytic enzymes, and the effects were determined through microscopic examination. Increase in optical density with the cessation of cyclosis, instantaneous collapse, lysis, disruption by cleavage, and the formation of protuberances followed by disruption were considered indicative of impairment in membrane structure. The similarity of response to RNAse, phosphodiesterase and pancreatin strongly suggests the presence of membrane RNA as an important constituent in the maintenance of structural integrity.     

Fluoro ketone inhibitors of hydrolytic enzymes

The use of fluoro ketones as inhibitors of hydrolytic enzymes has been investigated. The acetylcholine analogues 6,6-dimethyl-1,1,1-trifluoro-2-heptanone and 3,3-difluoro-6,6-dimethyl-2-heptanone are inhibitors of acetylcholinesterase with Ki values of 16 X 10(-9) M and 1.6 X 10(-9) M, respectively. These fluoro ketones are 10(4)-10(5) times better as inhibitors than the corresponding methyl ketone. Since nucleophiles readily add to fluoro ketones, it is likely that these compounds inhibit acetylcholinesterase by formation of a stable hemiketal with the active-site serine residue. Fluoro ketone substrate analogues are also inhibitors of zinc metallo- and aspartylproteases. 2-Benzyl-4-oxo-5,5,5-trifluoropentanoic acid is an inhibitor of carboxypeptidase A (Ki = 2 X 10(-7) M). Trifluoromethyl ketone dipeptide analogues are good inhibitors of angiotensin converting enzyme. An analogue of pepstatin that contains a difluorostatone residue in place of statine has been prepared and found to be an extremely potent inhibitor of pepsin (Ki = 6 X 10(-11) M). The hydrated ketones are probably the inhibitory species since they are structural mimics of the tetrahedral intermediate that forms during the hydrolysis of peptide substrates.     

粘细菌产生的水解酶类研究进展

粘细菌隶属于δ变形菌纲(Deltaproteobacteria),是重要的药源微生物类群,但是其分离培养困难,严重限制了粘细菌资源的发掘和开发利用。粘细菌是微生物捕食者,通过产生丰富多样的胞外水解酶,如淀粉酶、蛋白酶、几丁质酶、纤维素酶、磷酸酶、蛋白酶等来裂解其他微生物或分解纤维素等作为营养物质来源。目前,粘细菌分离纯化技术主要是利用被捕食菌或纤维素诱导法。可以说,粘细菌胞外水解酶是研究其分离培养方法的物质基础。然而,目前研究者们对粘细菌产生的水解酶类关注较少。本文主要对粘细菌产生的水解酶种类、性质及其功能进行归纳总结,为今后粘细菌分离培养技术和开发利用等相关研究提供参考。     

A note on the pectinolytic enzymes of Lachnospira multiparus

The identification of pectinolytic enzymes from two strains of Lachnospira multiparus grown on media containing pectin with differing degrees of methylation as the carbon source was investigated. Both pectinesterase and lyase activity were determined but there was no evidence of polygalacturonase being present as either an extracellular or intracellular enzyme.     

A note on stability of purified enzymes to dehydration

Highly purified enzymes from commercial sources were dried from aqueous solutions over CaCl₂ or CaSO₄ at 25° c, 4° c or −4° C. Several heat stable enzymes containing SS groups (chymotrypsin, lipase, pepsin and trypsin) retained most of their activity following drying while papain and ribonuclease retained about one-fourth of their original activity. Most SH containing enzymes lost most if not all activity during drying (catalase, hexokinase, glucose and xanthine oxidases, alcohol, glutamate, isocitrate and glucose-6-phosphate dehydrogenases). Lactic dehydrogenase was the exception in this group retaining 75% of its original activity after drying. Neither sucrose nor mannitol were effective in protecting ribonuclease against inactivation during drying. Temperature during drying had little effect on inactivation.     

Productivity of hydrolytic enzymes by mycorrhizal mushrooms

To survey the potential for production of extracellular hydrolytic enzymes by mycorrhizal mushrooms, productivities of these exo-enzymes from mycelia on potato-dextrose liquid medium were determined.Tricholoma matsutake produced relatively high levels of CM-cellulase and avicelase activities in all test strains. It also produced higher activity of acid proteinase than neutral proteinase. Its xylanase activities seemed to be higher than those of the other carbohydrases. The productivities ofLyophyllum shimeji strains were at similar levels to those ofT. matsutake strains. CM-cellulase and avicelase activities ofL. shimeji were higher than those ofT. matsutake. Neutral proteinase inL. shimeji strains showed higher activity levels than acid proteinase. The relative productivities of hydrolytic enzymes between the groups of mycorrhizal mushrooms and wood-rotting mushrooms were also examined.T. matsutake andL. shimeji both produce many kinds of hydrolytic enzymes in their culture broth, and the potential for production of hydrolytic enzymes by mycorrhizal mushrooms was judged to be relatively high.     

A comparative survey of the hydrolytic enzymes of ectoparasitic and free-living mites

Extracts of ectoparasitic mites of birds (Dermanyssus gallinae), sheep (Psoroptes ovis) and plants (Tetranychus urticae) and of free-living mites (Acarus siro) contained acid and alkaline phosphatase, C4 and C8 esterases, lipase, leucine and valine aminopeptidases and a range of glycosidase activities. Dermanyssus gallinae and P. ovis, species highly adapted to an animal parasitic lifestyle, had very similar profiles and contained low activities of glycosidases. In contrast, the polyphagous species A. siro contained moderate to high activities of every glycosidase examined, whereas the phytophagous species, T. urticae, displayed high activities of only beta-galactosidase and beta-glucuronidase. All extracts hydrolysed haemoglobin with optima below pH6, and this hydrolysis was associated with an aspartic proteinase and variable cysteine proteinase activity dependent on species. Inhibitor-labelling with biotinyl-Phe-Ala-FMK revealed the presence of cysteine proteinases with molecular masses of 25-33.5kDa. Each mite species contains the enzymes necessary to complete digestion of the diet in the intracellular lysosomal compartment. The absolute and relative activities of each enzyme varied, and are discussed according to phylogeny and dietary habit.