Different tartrate sensitivity and pH optimum for two isoenzymes of acid phosphatase in osteoclasts. An electron-microscopic enzyme-cytochemical study

Summary By differentiation of substrate specificity, pH optimum range, and sensitivity to various inhibitors, 2 isoenzymes of acid phosphatase in bone cells have been studied at the electron-microscopic level. When p-nitrophenyl phosphate was used for the substrate, the demonstrable enzyme activity was affected by neither tartrate nor sodium fluoride. The reaction product, when incubated at pH 5–6, was detected in all sites along the pathway for the biosynthesis of acid phosphatase in the osteoclast, including the perinuclear space, cisternae of the endoplasmic reticulum, Golgi complex, various vesicles, and vacuoles. In the osteoclasts attached to bone, the enzymatic activity was demonstrated at the extracellular ruffled border and on the eroded bone surface. Reaction products became confined to lysosomes and extracellular ruffled border when incubated at pH 6–7. Unattached osteoclasts showed a similar intracytoplasmic localization of enzyme as the attached ones, except for the absence of the extracellular enzyme activity. The mononuclear, immature type of osteoclast also resembled the mature osteoclast in terms of enzymatic localization. Except for the osteoclasts, the acid p-nitrophenyl phosphatase activity was restricted to lysosomal vesicles in various bone cells, monocytes, and macrophages. Such activity was inhibited by adding 50 mM tartrate to the p-nitrophenyl phosphate medium. When -glycerophosphate or p-nitrocatechol sulfate was the substrate, most of the reaction product was localized intracellularly. Unlike the acid p-nitrophenyl phosphatase, the acid -glycerophosphatase or arylsulfatase activity in osteoclasts and other bone cells was inhibited completely by 10 mM tartrate or 10 mM sodium fluoride. Even preincubation of 100 mM tartrate in the buffer inhibited -glycerophosphatase activity completely, but p-nitrophenyl phosphatase activity was inhibited incompletely. Consequently, our results suggest that acid p-nitrophenyl phosphatase is a useful cytochemical marker for identification of the osteoclast family at electron-microscopic levels of resolution.     

Quantification of the histochemical reaction for alkaline phosphatase activity using the indoxyl-tetranitro BT method

Summary The indoxyl—tetranitro BT method for the demonstration of alkaline phosphatase activity has been optimized and its validity for quantitative histochemistry tested. The study has been performed with model films of polyacrylamide gel incorporating homogenate of rat liver and with cryostat sections from the same livers. Addition of polyvinyl alcohol to the incubation medium greatly improved the localization of the final reaction product in cryostat sections. In polyacrylamide films, the formazan production specifically due to alkaline phosphatase was highest when using a medium containing 100mm Tris-HCl buffer, pH 9.0, 0.2–1.0mm substrate, 0.32mm 1-methoxyphenazine methosulphate, 10mm MgCl₂, 5mm sodium azide and 1mm tetranitro BT. For the incubation of cryostat sections in the presence of polyvinyl alcohol, the same medium could be used but the optimum concentrations of substrate and tetranitro BT appeared to be 1–2mm and 5mm respectively. The test minus control reaction was specific for alkaline phosphatase activity and could be inhibited completely with tetramisole. The test minus control reaction was linear with time up to 30 min with model films and up to 15 min with cryostat sections. The formazan production was also linear with the amount of homogenate incorporated in model films and with section thickness up to 18 µm and therefore, the reaction obeyed the Beer—Lambert law. Variation of the substrate concentration yielded aK _M of 0.05mm for aqueous media and aK _M of 0.55mm for polyvinyl alcohol-containing media. The inhibition with tetramisole appeared to be competitive withK _i = 0.07mm for aqueous media andK _i = 0.7mm for polyvinyl alcohol-containing media. These values indicate that the indoxyl—tetranitro BT method is considerably more sensitive than any metal salt or diazonium salt method developed so far. It is concluded that the optimized method described here is a specific, sensitive and valid quantitative histochemical method for the demonstration of alkaline phosphatase activity.     

A quantitative study of peroxidase activity in unfixed tissue sections of the guinea-pig thyroid gland

Summary A technique for the cytochemical demonstration of peroxidase activity in unfixed guinea-pig thyroid tissue is described in this paper. The substrate 3,3-diaminobenzidine tetrahydrochloride (DAB) is oxidized by the peroxidase to form an insoluble reaction product. Optimal results were obtained after 20 min incubation at 37° C in reaction medium containing 1.4mm DAB (in 0.1m Tris-HCl) and 0.15mm hydrogen peroxide at pH 8.0. Peroxidase activity was seen in the thyroid follicle cells as a diffuse brown reaction product (which was more dense and granular in erythrocytes). The enzyme activity was quantified using a scanning-integrating microdensitometer, and the effects of two specific peroxidase inhibitors were evaluated. Both 3-amino-1,2,4-triazole and methimazole inhibited peroxidase activity in the follicle cells (enzyme activity was still seen in the erythrocytes), maximal inhibition occurring at 10mm. Stimulation of peroxidase in the thyroid was observedin vivo (1 I.U. TSH administered every 8 h for two days), with the maximal stimulation occurring after 1 day.     

Is acid phosphatase activity present in bone matrix at sites of endochondral ossification in rabbit fracture callus?

It has been suggested that acid phosphatase activity is present in newly formed bone matrix at sites of endochondral ossification in rabbit fracture calluses. Because acid phosphatases are usually found intracellularly, it was decided to test this possibility more rigorously. Tissue from 10- and 14-day healing rabbit fractures was subjected to a series of critical tests for acid phosphatases with a pH optimum of 5.0. Fluoride, tartrate and molybdate were used as potential inhibitors of acid phosphatase activity. The effects of several counterstaining protocols were also investigated. A fluoride- and tartrate-resistant acid phosphatase is located in osteoclasts and mononuclear phagocytes. Diffuse staining of the bone matrix is seen, but it is dependent upon the length of incubation in the substrate medium and the distance from the acid phosphatase-reacting cells. It is concluded that the coloration of the bone matrix is probably caused by diffusion of the dye and reaction product and is, therefore, artifactual. © 1998 Chapman & Hall     

Strain improvement of Aspergillus niger for phytase production

A strain improvement program was developed to increase extracellular phytase (E.C. 3.1.3.8.) production by Aspergillus niger (syn. A. ficuum) NRRL 3135. Ultraviolet (UV) radiation was used as the mutagen and resistance to 50 g/ml of hygromycin B as the selection method. Mutant 2DE, the product of two UV treatments, had phytase (PhytA) activity at pH 5.0 in the extracellular filtrate that was 3.3-fold higher than the wild-type activity. The activity of the non-specific acid phosphatase with a pH optimum of 6.0 (Pase) was one-fifth the activity of the wild type and the non-specific acid phosphatase with a pH optimum of 2.5 (PhytB) was not significantly different from the wild type. The mutant and wild-type PhytA, PhytB and Pase responsed similarly in inhibition studies. However, the wild-type enzymes were inhibited more by 1 mm sodium fluoride and 1 mm phosphomycin. PhytA production by the mutant was repressed 60% by inorganic phosphate concentrations of 0.006% (wt/vol) or above. The mutant had an extracellular protein concentration 3.2-fold higher than the wild type, which correlated with its higher phytase activity at pH 5.0, but not with phytase activity at pH 2.5 and acid phosphatase activities. The isolate may be a phytase catalytic mutant, as well as, on overproducer of phytase. In addition, a mutant with an apparent lack of activity of all three acid phosphatases was isolated.Correspondence to: R. J. Wodzinski     

Histochemistry of hydrolytic enzymes in resting submandibular glands of rabbits

Summary The distribution of several hydrolytic enzymes was investigated in rabbit submandibular glands at both the light and electron microscopical levels. Glands were fixed by either immersion or perfusion fixation with a variety of fixatives containing 1–2% glutaraldehyde and 2–4% formaldehyde in 0.1m cacodylate buffer at pH 7.2. Light microscopically, the acinar cells showed some staining for ATPase, acid phosphatase and nonspecific esterases but showed weak staining for thiamine pyrophosphatase. Acid phosphatase staining occurred most strongly in granular tubule cells. Staining for esteroproteases was confined to the periluminal rims of intercalary and striated ducts. Alkaline phosphatase was very sensitive to glutaraldehyde and was confined to myoepithelial cells.Electron microscopical observations revealed the presence of acid phosphatase reaction product in lysosomes, immature granules and in GERL-like structures, the last being much more conspicuous in the granular tubule cells. ATPase reaction product was localized to the basal and luminal plasma membranes and lumina of both acinar and granular tubule cells. The Golgi complex of these two types of cells exhibited only moderate amounts of reaction product for thiamine pyrophosphatase. Alkaline phosphatase activity, on the other hand, was exclusively localized to myoepithelial cells in their plasma membranes and sometimes in the nuclear envelope.     

Structural characteristics of the saxitoxin receptor on nerve

Summary The effects of uranyl ion (UO ₂ ²⁺ ; at low concentrations binds specifically to phosphate groups) and the cationic dye methylene blue (MB⁺; binds strongly to carboxyl groups) on saxitoxin (STX) potency in crayfish axon has been studied by means of intracellular microelectrodes. At pH 6.00±0.05 and 13.5mm Ca²⁺, addition of 10.0 m UO ₂ ²⁺ +5.0nm STX had only slightly, if any, less effect on the spike's maximum rate of rise [0.79±0.04 (viz., mean±sem) of control value] than did addition of 5.0nm STX alone (0.72±0.05). Under the same conditions of pH and Ca²⁺ concentration, 1.0mm MB⁺ had approximately the same effect: 1.0mm MB⁺+5.0nm STX, 0.76±0.03; 5.0nm STX alone, 0.70±0.04. However, at pH 7.00±0.05 and lower Ca²⁺ concentrations, 1.0mm MB⁺ significantly reduced STX potency. Using 6.0mm Ca²⁺: 1.0mm MB⁺+5.0nm STX, 0.92±0.01; 5.0nm STX alone, 0.68±0.08. Using 3.0mm Ca²⁺, the corresponding values were 0.94±0.03 and 0.67±0.04. It is concluded that: (1) In accord with previous suggestions, the ionized acidic group known to exist in the Na channel (and to which a guanidinium group of STX appears to bind) is very likely a carboxyl group and not a phosphate group. (2) The accessible part of the Na channel mouth serving as the saxitoxin receptor probably does not include phospholipid in its structure proper.     

Protein phosphatase from rat liver nuclei

Summary Protein phosphatase, active on non-histone phosphoprotein substrate, was partially purified from rat liver cell nuclei by means of salt extraction, ammoniumsulfate precipitation, DEAE cellulose chromatography, gel filtration and preparative isoelectrofocusing.Rat liver nuclei contain a heterogenous population of different protein phosphatases. All the enzyme fractions eluted from DEAE cellulose are of low molecular weight between 12,000–31,000. The pH 5.5 peak fraction of preparative isoelectrofocusing was characterized in detail. It has a pH optimum of 6.8 using nuclear phosphoprotein substrate. It is inhibited by Na⁺ at 80mm, and to a lesser extent by K⁺, activated by Mg²⁺(5mm) and Mn²⁺ (1mm). However, the latter is inhibitory at 6mm.The nuclear protein phosphatase is also active on labelled F1 and F2b histones and casein, however, its V is lower on histones and it contains component(s) active specifically on nuclear phosphoprotein substrate but not on casein.Abbreviations PP-ase protein phosphat Part of this work was presented at the XI^th FEBS Meeting, Copenhagen 1977.     

A quantitative histochemical study of 5′-nucleotidase activity in rat liver using the lead salt method and polyvinyl alcohol

Summary 5-Nucleotidase (EC 3.1.3.5) activity was demonstrated in cryostat sections of rat liver using the Wachstein—Meisel medium and polyvinyl alcohol as tissue stabilizer. Optimum activity was obtained using an incubation medium containing 5mm AMP, 10mm magnesium chloride, 7.2mm lead nitrate, 0.1m Tris—maleate buffer, pH 7.2, and 17% (w/v) polyvinyl alcohol (Sigma, type III). The activity was localized at the bile canalicular and sinusoidal side of the plasma membranes of liver parenchymal cells as well as in the plasma membranes of endothelial cells of central veins and in fibroblasts surrounding portal tracts. The reaction was specific for 5-nucleotidase because it was inhibited by ADP. Alkaline phosphatase did not interfere in the reaction. Cytophotometric analysis revealed a linear relationship between the formation of the final reaction product and incubation times up to 20 min and section thicknesses up to 8m. The activity in pericentral zones was 1.35 times the activity in periportal zones. The Michaelis constant for AMP was 1.4mm in pericentral zones and 0.8mm in periportal zones, suggesting that the bile canalicular and sinusoidal enzymes differ in their kinetic characteristics.     

Ultrastructural localization of tartrate-resistant acid phosphatase (purple acid phosphatase) activity in chicken cartilage and bone.

Tartrate-resistant acid adenosine triphosphatase activity at pH 6.5, using a lead-salt method, was localized at light and electron microscopic levels in cartilage and bone matrices, osteoclasts, and chondroclasts. Cartilage matrix staining occurred after vascular invasion of the growth plate. In osteoclasts, activity was present in lysosomes, extracellular ruffled border channels, and the underlying cartilage and bone matrices. Staining artifacts occurred at lower pH levels (pH 5.4, 5.0). Adenosine diphosphate, p-nitrophenylphosphate, thiamine pyrophosphate, and alpha-naphthylphosphate also acted as substrates; but no activity was observed when adenosine monophosphate, adenylate-(beta, gamma-methylene) diphosphate, and beta-glycerophosphate were used. The activity was inhibited by NaF, dithionite, and a high concentration of p-chloromercuribenzoic acid, and activated by simultaneous addition of FeCl2 and ascorbic acid, as has been shown in biochemical studies. These histochemical results support the view that the adenosine triphosphate hydrolyzing activity at pH 6.5 is due to tartrate-resistant acid phosphatase (TRAP). There were some differences in ultrastructural localization between TRAP and tartrate-sensitive acid phosphatase (TSAP) activities in osteoclasts: TSAP activity was more intense in lysosomes and Golgi complexes and TRAP was stronger in the cartilage and bone matrices. It is suggested, therefore, that most of TRAP is in an inactive form in cells and is activated when secreted.     

Purification and some properties of a thermostable protease ofThermoactinomyces thalpophilus

Summary A thermostable protease fromThermoactinomyces thalpophilus was purified to give a single protein band on disc PAGE with a molecular size of 55000 Da. Optimal proteolytic activity of the purified protease was at pH 6.0 and 70°C. The enzyme was maximally stable between pH 5.0 and 8.0 and retained 62% of its original activity at 70°C after 30 min. Temperature stability was not improved in the presence of Ca²⁺ (1mm). Enzyme activity was inhibited by AG⁺, Hg²⁺, Ba²⁺ and Co²⁺, partially inhibited byo-phenanthroline but not by diisopropylfluorophosphate (5mm).

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Resumen Se purificó una proteína termoestable deThermoactinomyces thalpophilus que dió una sola banda proteica al someterla a una electroforesis en columna de poliacrilamida (PAGE) y un tamaño molecular de 55.000 Da. La actividad proteolítica de la proteína purificada era óptima a pH 6.0 y 70°C. El enzima tenía máxima estabilidad entre pH 5.0 y 8.0 y retuvo un 62% de su actividad original despues de 30 min at 70°C. La estabilidad térmica no mejoró en presencia de Ca²⁺ (1mm). La actividad enzimática fue Inhibida por Ag⁺

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Résumé Une protéase thermostable deThermoactinomyces thalpophilus a été purifiée jusqu'à donner une bande protéique unique sur un disque PAGE avec un poids moléculaire de 55000 daltons. L'activé protéolytique optimum de la protéase purifiée se situe à pH 6.0 at à 70°C. L'enzyme présente son maximum de stabilité entre pH 5.0 et 8.0 et conserve 62% de son activité originelle après 30 min à 70°C. La stabilité à la température n'est pas améliorée en présence de Ca²⁺ 1mm. L'activité enzymatique est inhibée par Ag⁺, Hg²⁺, Ba²⁺ et Co²⁺. Elle est partiellement inhibée par l'o-phénanthroline mais elle n'est pas inhibée par le di-iso-propylfluorophosphate 5mm.

     

Coupled Na+/H+ exchange in rat parotid basolateral membrane vesicles

Summary pH gradient-dependent sodium transport in highly purified rat parotid basolateral membrane vesicles was studied under voltage-clamped conditions. In the presence of an outwardly directed H⁺ gradient (pH_in=6.0, pH_out=8.0)²²Na uptake was approximately ten times greater than uptake measured at pH equilibrium (pH_in=pH_out=6.0). More than 90% of this sodium flux was inhibited by the potassium-sparing diuretic drug amiloride (K ₁ =1.6 m) while the transport inhibitors furosemide (1mm), bumetanide (1mm) SITS (0.5mm) and DIDS (0.1mm) were without effect. This transport activity copurified with the basolateral membrane marker K⁺-stimulatedp-nitrophenyl phosphatase. In addition²²Na uptake into the vesicles could be driven against a concentration gradient by an outwardly directed H⁺ gradient. pH gradient-dependent sodium flux exhibited a simple Michaelis-Menten-type dependence on sodium concentration cosistent with the existence of a single transport system withK _M =8.0mm at 23°C. A component of pH gradient-dependent, amiloride-sensitive sodium flux was also observed in rabbit parotid basolateral membrane vesicles. These results provide strong evidence for the existence of a Na⁺/H⁺ antiport in rat and rabbit parotid acinar basolateral membranes and extend earlier less direct studies which suggested that such a transporter was present in salivary acinar cells and might play a significant role in salivary fluid secretion.     

Chick osteoblasts contain fluoride-sensitive acid phosphatase activity

We used histological and biochemical methods to determine the cellular origin of bone matrix fluoride-sensitive acid phosphatase in chicken bone. Embryonic chicken calvariae were embedded in plastic and sections stained for acid phosphatase at various concentrations of substrate and fluoride. Acid phosphatase activity was observed in osteoblasts and osteoclasts but not in fibroblasts. Striking inhibition of osteoblastic acid phosphatase occurred at 100 microM fluoride, a concentration that had no apparent effect on osteoclastic acid phosphatase. Inhibition of osteoblastic and osteoclastic acid phosphatase by fluoride was also examined using extracts of embryonic chicken calvarial cells, mouse osteoblasts (MC3T3-El cell line), and purified chick osteoclasts, respectively. Fluoride is a partial competitive inhibitor of both chicken and mouse osteoblastic acid phosphatases, with apparent inhibition constants of 10-100 microM. These concentrations of fluoride correspond to those that increase bone formation in vitro and in vivo. In contrast, the apparent inhibition constant for fluoride of osteoclastic acid phosphatase was much higher (i.e., 0.5 mM). In summary, this study demonstrates that chicken osteoblasts contain an acid phosphatase that is sensitive to inhibition by low concentrations (i.e., microM) of fluoride.     

Histochemical distribution of potassium-dependent p-nitrophenylphosphatase in the calf intestine

Summary Potassium-dependentp-nitrophenylphosphatase was demonstrated, using the lead citrate method of Mayaharaet al. (1980), in frozen sections of calf intestine fixed in formalin-calcium. The calcium chloride included in the fixative was shown to improve the localization of the reaction markedly. The phosphatase activity observed in the basolateral cell borders of the surface epithelium in the small intestine and colon was reduced by 10mm oubain and by substitution of sodium ions for potassium ions, confirming that the reaction was representative for the second step in the Na⁺/K⁺-ATPase complex. The intensity of the basolateral enzyme reaction was in the order: colon > duodenum, proximal jejunum > ileum > middle and distal jejunum. The crypts reacted weakly. A reaction in the brush border of the proximal jejunum and duodenum and a granular reaction in the supranuclear cytoplasm of the epithelial cells was not influenced by oubain. The staining pattern for the potassium-dependent phosphatase differed from that of alkaline phosphatase and Mg²⁺-dependent ATPase, which gave a reaction that was restricted to the brush border.     

Cytochemical demonstration of increased adenosine triphosphatase activity in lymphocytes activated in vitro by phytohaemagglutinin or by the mixed lymphocyte reaction

Summary Cytochemical investigations of ATPase activity were performed on lymphocytes isolated from peripheral blood and activatedin vitro by phytohaemagglutinin or by the two-way mixed lymphocyte reaction. Uncultured lymphocytes showed very little activity localized in small granules. The activity increased markedly during transformation. In fully transformed and actively proliferating cells, the ATPase activity was intense and localized in a crescentic perinuclear area of cytoplasm which was pale-staining and vesicular in Giemsa-stained preparations. In mitotic cells, the activity was in discrete granules or elongated structures suggestive of mitochondria, scattered throughout the cytoplasm. The ATPase activity had a pH optimum of 8.5 to 9.5 and was strongly inhibited at pH 7.5. The activity was stimulated by Ca²⁺ and Mg²⁺ and was inhibited byp-chloromercuribenzoate but not by oligomycin, which appeared to enhance the reaction. Lead nitrate at a concentration of 3mm did not inhibit the reaction.     

An ultrastructural study of phosphatases and aryl sulphatase in BHK and CHO cells grown in culture

Summary The ultrastructural distribution of a number of phosphatases and aryl sulphatase has been studied in BHK 21/C 13, BHK21/J 1 and CHO cells grown in culture. In all three cell lines acid -glycerophosphatase and aryl sulphatase appear to be confined to lysosomes and elements of the Golgi apparatus and glucose-6-phosphatase to the endoplasmic reticulum. With thiamine pyrophosphate at pH 7.0 in CHO cells reaction product is present in lysosomes, the Golgi apparatus, the endoplasmic reticulum and on the cell surface. Preincubation at acid pH reduces the reactions in the endoplasmic reticulum but enhances the surface activity. At pH 5.0 and pH 7.0 in CHO cells p-nitrophenylphosphatase is present in lysosomes, the Golgi apparatus and the endoplasmic reticulum and this activity is inhibited by sodium fluoride. p-nitrophenylphosphatase activity is also present on the cell surface of CHO cells and this activity is not inhibited by sodium fluoride. No activity could be demonstrated in any cells at pH 9.O. The significance of these results is discussed with respect to the possible role of surface acid phosphatase in the process of transformation.     

Purification and characterization of glutamine synthetase from the commerical mushroom Agaricus bisporus

Agaricus bisporus glutamine synthetase, a key enzyme in nitrogen metabolism, was purified to apparent homogeneity. The native enzyme appeared to be a GS-II type enzyme. It has a molecular weight of 325 kDa and consists of eight 46-kDa subunits. Its pI was found at 4.9. Optimal activity was found at 30°C. The enzyme had low thermostability. Stability declined rapidly at temperatures above 20°C. The enzyme exhibits a K _m for glutamate, ammonium, and ATP of 22mm, 0.16mm and 1.25mm respectively in the biosynthetic reaction, with optimal activity at pH 7. The enzyme is slightly inhibited by 10mm concentrations of l-alanine, l-histidine, l-tryptophan, anthranilic acid, and 5-AMP and was strongly inhibited by methionine sulfoximine and phosphinothricine. For the transferase reaction K _i-values were 890 m and 240 m for methionine sulfoximine and phosphinothricine respectively. For the biosynthetic reaction K _i was 17 m for both methionine sulfoximine and phosphinothricine.     

Partial purification and some properties of an alkaline cellulase from an alkalophilic Bacillus sp.

A newly isolated Bacillus species, which grew optimally at 30°C and pH 10, produced a carboxymethylcellulase in a medium containing 10 g CM-cellulose/l. The enzyme, when partially purified by gel filtration, had a mass of about 29 kDa as determined by both SDS-PAGE and gel filtration chromatography. It was optimally active at pH 9.5 and 40°C, and was stable from pH 7 to 11 at 4°C for 24 h. The enzyme was stimulated by Ca²⁺ (1mm) but was completely inhibited by Hg²⁺ (1mm). Neither EDTA nor EGTA (10mm) affected the activity.The author is with the Department of Biological Sciences, University of Jordan. PO Box 2686, Amman 11181, Jordan     

Production and characterization of polygalacturonase fromGeotrichum candidum

An extracellular polygalacturonase (EC 3.2.1.15) fromGeotrichum candidum ATCC 34614 grown onsauerkraut brine was produced and characterized. Polygalacturonic acid markedly increased the enzyme yield in the brine. The fungus produced the highest activity (290 U/l) in brine with 0.3% (w/v) polygalacturonic acid. The pH and temperature optima of the enzymes were 4.5 to 5.0 and 30°C, respectively. It was stable from pH 4.0 to 5.8 and at 30°C but lost its activity at higher temperatures. The K_m and V_max values for polygalacturonic acid were 4.2 mg/ml and 0.19mm galacturonic acid/min, respectively. The enzyme was not substrate inhibited.     

Purification and characterization of invertase from Aspergillus niger

Invertase produced by a strain of Aspergillus niger showed the following main characteristics: maximum activity at 60°C, pH 5.0; K _m with sucrose as substrate, 0.0625mm; V _max 0.013 mol/min; and free energy 9132 cal/mol. The metal ions and p-chloromercuribenzoate (PCMB) acted as inhibitors respectively.