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1.
Purification and partial characterization οf a new β-xylosidase from
Humicola grisea var. thermoidea
T. Iembo M.O. Azevedo C. Bloch Jr. E.X.F. Filho 《World journal of microbiology & biotechnology》2006,22(5):475-479
Summary The thermophilic fungus Humicola grisea var. thermoidea produces a mycelium-associated β-xylosidase activity when grown in liquid-state cultures on media containing oat spelt xylan
as the carbon source. The β-xylosidase was purified to apparent homogeneity by gel filtration and anion exchange chromatography.
Its molecular weight was 37 and 50 kDa, as determined by MALDI/TOF mass spectrometry and SDS-PAGE, respectively. The purified
enzyme exhibited maximum activity at 55 °C and pH 6.5. It was also active at pH 8.8, retaining 60% of its activity after 6 h
of incubation at 50 °C. β-xylosidase was strongly inactivated by NBS and slightly activated by DTT and β-mercaptoethanol.
The enzyme was highly specific for PNPX as the substrate. The purified β-xylosidase showed K
m and V
max values of 1.37 mM and 12.98 IU ml−1, respectively. 相似文献
2.
Purification and characterization of an ADP-dependent phosphofructokinase from Thermococcus zilligii 总被引:1,自引:0,他引:1
R. S. Ronimus Jurre Koning H. W. Morgan 《Extremophiles : life under extreme conditions》1999,3(2):121-129
The ADP-dependent phosphofructokinase (PFK) from Thermococcus zilligii has been purified 950 fold; it had a specific activity of 190 U mg−1. The enzyme required Mg2+ ions for optimal activity and was specific for ADP. The forward reaction kinetics were hyperbolic for both cosubstrates (pH
optimum of 6.4), and the apparent K
m values for ADP and fructose-6-phosphate were 0.6 mM (apparent V
max of 243 U mg−1) and 1.47 mM (apparent V
max of 197 U mg−1), respectively. Significantly, the enzyme is indicated to be nonallosteric but was slightly activated by some monovalent
cations including Na+ and K+. The protein had a subunit size of 42.2 kDa and an estimated native molecular weight of 66 kDa (gel filtration). Maximal
reaction rates for the reverse reaction were attained at pH 7.5–8.0, and the apparent K
m values for fructose-1,6-bisphosphate and AMP were 0.56 mM (apparent V
max of 2.9 U mg−1) and 12.5 mM, respectively. The biochemical characteristics of this unique ADP-dependent enzymatic activity are compared
to ATP and pyrophosphate-dependent phosphofructokinases.
Received: August 14, 1998 / Accepted: December 2, 1998 相似文献
3.
A thermophilic Bacillus sp. was isolated that secreted an extracellular, thermostable lipolytic enzyme. The enzyme was purified to 58 folds with
a specific activity of 9730 units/mg of protein and yield of 10% activity by ammonium sulphate precipitation, Phenyl Sepharose
chromatography, gel-permeation followed by Q Sepharose chromatography. The relative molecular mass of the protein was determined
to be 61 kDa by SDS-PAGE and approximately 60 kDa by gel permeation chromatography. The enzyme showed optimal activity at
60–65 ∘C and retained 100% activity after incubation at 60 ∘C and pH 8.0 for 1 h. The optimum pH was determined to be 8.5. It exhibited 50% of its original activity after 65 min incubation
at 70 ∘C and 23 min incubation at 80 ∘C. Catalytic function of lipase was activated by Mg++ (10 mM), while mercury (10 mM) inactivated the enzyme completely. No effect on enzyme activity was observed with trypsin
and chymotrypsin treatment, while 50% inhibition was observed with thermolysin. It was demonstrated that PMSF, SDS, DTT, EDTA,
DEPC, βME (100 mM each) and eserine (10 mM) inhibited the activity of the lipolytic enzyme. With p-nitrophenyl laurate as
a substrate, the enzyme exhibited a K
m
and V
max of 0.5 mM and 0.139 μM/min/ml. The enzyme showed preference for short chain triacylglycerol and hydrolyzes triolein at all
positions. In contrast to other thermostable Bacillus lipases, this enzyme has very low content of hydrophobic amino acids (22.58 %). Immunological studies showed that the active
site and antigen-binding site of enzyme do not overlap. 相似文献
4.
We have investigated conditions leading to the degradation of glycinebetaine in Aphanothece halophytica and have shown the activity of betaine-homocysteine methyltransferase (BHMT). The intracellular glycinebetaine level was
decreased approximately 50% after 36 h salt downshock from 2.0 m NaCl medium to 0.5 m NaCl medium. A slight additional decrease
of glycinebetaine occurred when salt downshock was combined with dark treatment. The omission of carbon and nitrogen sources
in the growth medium further decreased intracellular glycinebetaine. The activity of BHMT increased from 0 to 460 nmol h−1mg−1 after 3 h salt downshock. Higher strength of salt downshock resulted in higher activity of the enzyme. Small increase of
the enzyme activity was also observed when A. halophytica was deprived of carbon and nitrogen sources in the growth medium.
Received: 17 March 2000 / Accepted: 24 April 2000 相似文献
5.
A ureidoglycolate-degrading activity was analysed in different tissues of French bean (Phaseolus vulgaris L.) plants during development. Activity was detected in all the tissues analysed, although values were very low in seeds before germination and in cotyledons. After radicle emergence, the activity increased due to high activity present in the axes. The highest levels of specific activity were found in developing fruits, from which the enzyme was purified and characterised. This is the first ureidoglycolate-degrading activity that has been purified to homogeneity from a ureide legume. The enzyme was purified 280 fold, and the specific activity for the pure enzyme was 4.4 units mg−1, which corresponds to a turnover number of 1,055 min−1. The native enzyme has a molecular mass of 240 kDa and consists of six identical or similar-sized subunits each of 38 kDa. The activity of the purified enzyme was completely dependent on manganese and asparagine. The enzyme exhibited hyperbolic, Michaelian kinetics for ureidoglycolate with a K
m value of 3.9 mM. This enzyme has been characterised as a ureidoglycolate urea-lyase (EC 4.3.2.3). 相似文献
6.
Employing the techniques of (NH4)2SO4 fractionation, ion exchange chromatography on DEAE cellulose and gel filtration through Sephadex G-100, pectinmethylesterase
(EC 3.1.1.11) was purified from guava (Psidium guajava L.) fruits var. Hisar Safeda harvested at turning stage of maturity to 129-fold with 28% recovery. Molecular weight as determined
by gel filtration was found to be 51 kDa and the enzyme preparation exhibited the same molecular weight under native (Native-PAGE)
and denaturating conditions (SDS-PAGE) indicating that the enzyme was a monomer. With pectin as the substrate, it exhibited
the Michaelis Menten kinetics with K
m value of 3.1 g l−1. The enzyme was found to be stimulated by Ca++ and Na+ and inhibited competitively by d-galacturonic acid with K
i
value of 1.97 mM. The enzyme was completely inactivated by iodine while with diethyl pyrocarbonate and N-acetylimidazole, the enzyme was inhibited up to the extent of 56 and 45%, respectively. However, DTNB had no inhibitory effect
whatsoever precluding the participation of any –SH group in the active centre. It is tentatively proposed that the enzyme
has tyrosine and histidine residues at its active centre. 相似文献
7.
Dihydroorotase was purified to homogeneity fromPseudomonas putida. The relative molecular mass of the native enzyme was 82 kDa and the enzyme consisted of two identical subunits with a relative
molecular mass of 41 kDa. The enzyme only hydrolyzed dihydro-l-orotate and its methyl ester, and the reactions were reversible. The apparentK
m andV
max values for dihydro-l-orotate hydrolysis (at pH 7.4) were 0.081 mM and 18 μmol min−1 mg−1, respectively; and those forN-carbamoyl-dl-aspartate (at pH 6.0) were 2.2 mM and 68 μmol min−1 mg−1, respectively. The enzyme was inhibited by metal ion chelators and activated by Zn2+. However, excessive Zn2+ was inhibitory. The enzyme was inhibited by sulfhydryl reagents, and competitively inhibited byN-carbamoylamino acids such asN-carbamoylglycine, with aK
i value of 2.7 mM. The enzyme was also inhibited noncompetitively by pyrimidine-metabolism intermediates such as dihydrouracil
and orotate, with aK
i value of 3.4 and 0.75 mM, respectively, suggesting that the enzyme activity is regulated by pyrimidine-metabolism intermediates
and that dihydroorotase plays a role in the control of pyrimidine biosynthesis. 相似文献
8.
Purification and properties of betaine aldehyde dehydrogenase from<Emphasis Type="Italic"> Avena sativa</Emphasis> 总被引:3,自引:0,他引:3
Livingstone JR Maruo T Yoshida I Tarui Y Hirooka K Yamamoto Y Tsutui N Hirasawa E 《Journal of plant research》2003,116(2):133-140
Betaine aldehyde dehydrogenase (BADH; EC 1.2.1.8) is the enzyme that catalyzes the second step in the synthesis of the osmoprotectant,
glycine betaine. NAD-dependent BADH was purified from Avena sativa shoots by DEAE Sephacel, hydroxyapatite, 5′-AMP Sepharose 4B, Mono Q and TSK-GEL column chromatographies to homogeneity by
the criterion of native PAGE, and the properties of BADH were compared with those of aminoaldehyde dehydrogenase purified
to homogeneity from A. sativa. The molecular mass estimated by both gel filtration using TSK-GEL column and Sephacryl S-200 was 120 and 115, kDa, respectively.
The enzyme is a homodimer with a subunit molecular mass of 61 kDa as shown by SDS-PAGE. The pI value of the enzyme was found
to be 6.3. The purified enzyme catalyzed not only the oxidation of betaine aldehyde (BAL), but also that of aminoaldehydes,
3-aminopropionaldehyde (APAL), 4-aminobutyraldehyde (ABAL), and 4-guanidinobutyraldehyde (GBAL). The K
m values for BAL, APAL, ABAL and GBAL were 5×10−6, 5.4×10−7, 2.4×10−5 and 5×10−5 M, respectively. APAL showed substrate inhibition at a concentration of 0.1 mM. A fragment of BADH cleaved by V8 protease
shared homology with other plant BADHs.
Electronic Publication 相似文献
9.
El-Sayed AS 《Journal of microbiology (Seoul, Korea)》2011,49(1):130-140
L-Methioninase was purified to electrophoretic homogeneity from cultures of Aspergillus flavipes using anion-exchange and gel filtration chromatography by 12.1 fold compared to the crude enzyme preparation. The purified
enzyme had a molecular mass of 47 kDa under denaturing conditions and an isoelectric point of 5.8 with no structural glycosyl
residues. The enzyme had optimum activity at pH 7.8 and pH stability from 6.8–8.0 at 35°C. The enzyme appeared to be catalytically
stable below 40°C. The enzyme activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol,
Hg+, Cu2+, and Fe2+, with slight inhibition by Triton X-100. A flavipes L-methioninase has a higher catalytic affinity towards L-methionine (Km, 6.5 mM and Kcat, 14.1 S−1) followed by a relative demethiolating activity to L-homo-cysteine (Km, 12 mM and Kcat, 9.3 S−1). The enzyme has two absorption maxima at 280 and 420 nm, typical of other PLP-enzymes. Apo-L-methioninase has the ability
to reconstitute its structural catalytic state completely upon addition of 0.15 mM PLP. L-Methioninase has neither an appreciable
effect on liver function, platelet aggregation, nor hemolysis of human blood. The purified L-methioninase from solid cultures
of A. flavipes displayed unique biochemical and catalytic properties over the currently applied Pseudomonad enzyme. 相似文献
10.
A recombinant β-galactosidase from Caldicellulosiruptor saccharolyticus was purified with a specific activity of 211 U mg−1 by using heat treatment and His-trap affinity chromatography. The native enzyme was an 80-kDa trimer with a molecular mass
of 240 kDa. Maximum activity was observed at pH 6.0 and 80oC, and the half-life at 70oC was 48 h. The enzyme exhibited hydrolytic
activity for p-nitrophenyl-β-d-galactopyranoside (pNPGal), oNPGal, or lactose, whereas no activity for p-nitrophenyl-β-d-glucopyranoside (pNPGlu), oNPGlu, or cellobiose. The catalytic residues E150 and E311 of β-galactosidase from C. saccharolyticus were completely conserved in all aligned glycoside hydrolase family 42 β-galactosidases. The results indicated that the enzyme
was a β-galactosidase. Galactose uncompetitively inhibited the enzyme. Glucose inhibition of the enzyme was the lowest among
β-galactosidases. When 50 g l−1 galactose was added, the enzyme activity for pNPGal was reduced to 26%. When 400 g l−1 glucose instead of galactose was added, the activity was reduced to 82%. When adding galactose (200 g l−1), only 14% of the lactose was hydrolyzed after 180 min. In contrast, the addition of glucose (400 g l−1) did not affect lactose hydrolysis, and more than 99% of the lactose was hydrolyzed after 120 min. 相似文献
11.
F. -M. Zhu B. Du H. -S. Gao C. -J. Liu J. Li 《Applied Biochemistry and Microbiology》2010,46(6):626-632
Protoplasts of Aspergillus oryzae 3.481 and Aspergillus niger 3.316 were prepared using cellulose and snail enzyme with 0.6 M NaCl as osmotic stabilizer. Protoplast fusion has been performed
using 35% polyethylene glycol 4,000 with 0.01 mM CaCl2. The fused protoplasts have been regenerated on regeneration medium and fusants were selected for further studies. An intracellular
(β-glucosidase (EC 3.2.1.21) was purified from the protoplast fusant of Aspergillus oryzae 3.481 and Aspergillus niger 3.316 and characterized. The enzyme was purified 138.85-fold by ammonium sulphate precipitation, DE-22 ion exchange and Sephadex
G-150 gel filtration chromatography with a specific activity of 297.14 U/mg of protein. The molecular mass of the purified
enzyme was determined to be about 125 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme
had an optimum pH of 5.4 and temperature of 65°C, respectively. This enzyme showed relatively high stability against pH and
temperature and was stable in the pH range of 3.0–6.6. Na+, K+, Ca2+, Mg2+ and EDTA completely inhibited the enzyme activity at a concentration of 10 mM. The enzyme activity was accelerated by Fe3+. The enzyme activity was strongly inhibited by glucose, the end product of glucoside hydrolysis. The K
m and V
max values against salicin as substrate were 0.035 mM and 1.7215 μmol min−1, respectively. 相似文献
12.
Qianqian Wu Min Zhang Ke Wu Bin Liu Jingmin Cai Renrui Pan 《Journal of applied phycology》2011,23(2):197-203
Dendryphiella arenaria TM94 is an obligate marine fungus. Fucoidanase expressed by TM94 by solid state fermentation was purified. The fermented
solid medium was extracted with citric acid buffer, and the extracts were precipitated by acetone and separated on Sephadex
G-100 chromatography. The specific fucoidanase activity of purified enzyme was 27-fold than that of the crude enzyme. The
recovery of the enzyme was 17.69%. SDS-PAGE was used to identify the purity and the molecular weight of the fucoidanase. A
single band appeared on SDS-PAGE gel which suggested that relatively pure fucoidanase has been obtained. The molecular weight
of fucoidanase is 180 kDa and the isoelectric point was about pH 4.4. The purified fucoidanase appeared to have the maximum
enzymatic activity at pH 6.0. KM and the maximum velocity of the enzyme was 6.56 mg·mL−1 and 6.55 mg·mL−1·min−1 by using fucoidan from Fucus vesiculosus as substrate. The enzyme may be a type of endo-fucoidanase which could hydrolyze high molecular weight fucoidan to low molecular
weight fucoidan rather than to fucose. 相似文献
13.
Marine bacterial isolates were screened for phospholipase C (PLC) activity on PCY agar plates containing phosphatidylcholine
(PC) as substrate. The strain that showed the highest activity on a PCY screening agar plate and a thin-layer chromatography
was identified as a strain of Pseudoalteromonas and subsequently designated Pseudoalteromonas sp. J937. The extracellular PLC of the strain J937 was purified to a specific activity of 33 U mg−1 protein by serial ion exchange and gel filtration column chromatography. It had a molecular mass of 32 kDa estimated by SDS–PAGE.
The optimal pH and temperature of the enzyme were about pH 8 and 45°C, respectively. The PLC hydrolyzed phosphatidylethanolamine
as well as PC but not other glycerophospholipids. Its activity was enhanced by 150% with Ca2+ (200 mM) and by 180% with Na+ (500 mM), suggesting that the purified PLC is a marine-type enzyme. 相似文献
14.
Trichoderma species are readily isolated from Brazilian cerrado soil by conventional methods and some of them were characterized as Trichoderma koningii. The effect of carbon source on the production of β-1,3-glucanases in the culture filtrates of a specific Trichoderma koningii strain (ALL 13) was investigated. Enzyme activity was detected in all carbon sources tested and only one band of β-1,3-glucanase
was detected in non-denaturing PAGE. This enzyme was purified by Sephacryl S-200 gel filtration and Phenyl Sepharose CL 4B
chromatography. A typical procedure provided 105-fold purification with 13.4% yield. The molecular weight of the purified
enzyme was 75 kDa as estimated by SDS-PAGE. The enzyme hydrolyzed laminarin in an endo-like fashion to form small oligosaccharides
and glucose. The Km and Vmax values for β-1,3-glucanase, using laminarin as substrate, were 0.148 mg.mL−1 and 0.159 U.min−1, respectively. The pH optimum for the enzyme was pH 4.6 and maximum activity was obtained at 50°C. Hg2+ inhibited the purified enzyme. 相似文献
15.
A nitrilase gene from Alcaligenes sp. ECU0401 was cloned and overexpressed in Escherichia coli BL21 (DE3) in a soluble form. The encoded protein with a His6-tag was purified to nearly homogeneity as revealed by SDS-PAGE with a molecular weight of approximately 38.5 kDa, and the
holoenzyme was estimated to be composed of 10 subunits of identical size by size exclusion chromatography. The V
max and K
m parameters were determined to be 27.9 μmol min−1 mg−1 protein and 21.8 mM, respectively, with mandelonitrile as the substrate. The purified enzyme was highly thermostable with
a half life of 155 h at 30 °C and 94 h at 40 °C. Racemic mandelonitrile (50 mM) could be enantioselectively hydrolyzed to
(R)-(−)-mandelic acid by the purified nitrilase with an enantiomeric excess of 97%. The extreme stability, high activity and
enantioselectivity of this nitrilase provide a solid base for its practical application in the production of (R)-(−)-mandelic acid. 相似文献
16.
Ming Xing Huang Yun Ye Ya Xiong Chen Ya Li Han 《International journal of peptide research and therapeutics》2012,18(2):153-161
Two proteins with fibrinolytic activity were partially purified from yellow mealworm (Tenebrio molitor) by ammonium sulfate precipitation between 30 and 70% saturation, gel filtration on Sephacryl-S200-HR, ion exchange chromatography
on DEAE-Sepharose-FF and metal chelate on Cu–HiTrap–IMAC–FF, but the enzymes had not been completely separated from each other.
The two partially purified fibrinolytic enzymes were designated as TMFE-I and TMFE-II (Tenebrio molitor fibrinolytic enzyme) with molecular weights of 27.5 and 24.9 kDa by SDS-PAGE individually. The partially purified solution
of TMFE-I and TMFE-II was considerably stable in the range of pH 5–10 and characterized by pH optimum of the enzymatic activity
at 8.0. Thermal stability of TMFE was excellent at 45°C and below. The K
M value was 0.26 mM for amidolysis of Bz–Arg–pNA. According to inhibitor analysis by fibrin plate method, phenylmethylsulfonyl
fluoride and tosyl-lysine chloromethyl ketone inactivated TMFE almost completely, but trans-(epoxysuccinyl)-l-leucylamino-4-guanidinobutane (E-64) and EDTA had little effect on their fibrinolytic activity. According to metal ion analysis
by fibrin plate method, the effect of metal ions on activity of TMFE showed a great difference. Na+, K+ and Zn2+ had little effect on the activity of TMFE. Mg2+ and Cu2+ showed inhibition effect on the fibrinolytic activity of TMFE, but Ca2+ increased the fibrinolytic activity of TMFE at final concentration varying from 0 to 30 mM. 相似文献
17.
A thermostable esterase from the hyperthemophilic archaeonSulfolobus solfataricus was partially purified 590-fold with 16.2% recovery. The partially purified esterase had a specific activity of 29.5μmol
min−1 mg−1 when the enzyme activity was determined usingp-nitrophenyl butyrate as a substrate. The apparent molecular weight was about 100 kDa, while the optimum temperature and pH
for esterase were 75°C and 8.0, respectively. The enzyme showed high thermal stability and solvent tolerance in comparison
to its mesophilic counterpart. The enzyme also showed chiral resolution activity for (S)-ibuprofen, indicating thatS. solfataricus esterase can be used for the production of commercially important chiral drugs. 相似文献
18.
A highly selective sucrose isomerase (SIase) was purified to homogeneity from the cell-free extract of Erwinia rhapontici NX-5 with a recovery of 27.7% and a fold purification of 213.6. The purified SIase showed a high specific activity of 427.1 U mg−1 with molecular weight of 65.6 kDa. The K
m for sucrose was 222 mM while V
max was 546 U mg−1. The optimum pH and temperature for SIase activity were 6.0 and 30 °C, respectively. The purified SIase was stable in the
temperature range of 10–40 °C and retained 65% of the enzyme activity after 2 weeks’ storage at 30 °C. The SIase activity
was enhanced by Mg2+ and Mn2+, inhibited by Ca2+, Cu2+, Zn2+, and Co2+, completely inhibited by Hg2+ and Ag2+. The purified SIase was strongly inhibited by SDS, while partially inhibited by dimethylformamide, tetrahydrofuran, and PMSF.
Additionally, glucose and fructose acted as competitive inhibitors for purified SIase. 相似文献
19.
Clostridium acetobutylicum P262 cells that were
growing on lactate and acetate had an NAD-independent lactate dehydrogenase
(iLDH) activity of 200 nmol mg protein−1 min−1.
Ammonium sulfate precipitation and DEAE cellulose caused a 35-fold
purification. Gel filtration indicated that the iLDH had a molecular weight
of approximately 55 kDa, but two bands were always observed. Phenyl sepharose
could not separate the two proteins, and hydroxyapatite caused a complete
loss of activity. The semi-purified iLDH had a Vmax of 13,000 nmol
mg protein−1 min−1 and a K
m
value of 3.5 mM for D-lactate. The Vmax and K
m
values for L-lactate were 300 nmol mg protein−1
min−1 and 0.7 mM. The iLDH had a pH optimum of 7.5, was not
activated by fructose-1,6-bisphosphate (FDP), and could be coupled to either
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) or
dichlorophenol-indophenol (DCPIP), but not methyl viologen (MV) or benzyl
viologen (BV). The iLDH did not have strong absorbance between 500 and 300
nm, and trichloroacetic acid or acid ammonium sulfate extracts had virtually
no fluorescence at 450 nm. The crude extracts also had MTT-linked butyryl-CoA
dehydrogenase activity (60 nmol mg protein−1
min−1). The NAD-independent butyryl-CoA dehydrogenase eluted
from DEAE-cellulose as two fractions. The yellow fraction was extremely
unstable, but the green fraction could be stored for short periods of time at
5°C. The green-colored butyryl-CoA dehydrogenase had strong absorption at
450 nm, and gel filtration indicated that it had a molecular weight of 90
kDa. The NAD-independent butyryl-CoA dehydrogenase could be coupled to MTT,
DCPIP, or MV, but not BV. Because the NAD-independent lactate and butyryl-CoA
dehydrogenase could both be linked to low potential carriers, these two
enzymes may function as oxidation-reduction system in vivo.
Received: 24 July 1996 / Accepted: 10 September 1996 相似文献
20.
S M Kotwal M M Gote M I Khan J M Khire 《Journal of industrial microbiology & biotechnology》1999,23(1):661-667
The thermophilic fungus Humicola sp constitutively produces intracellular α-galactosidase (1.33 U mg−1 protein) within 48 h at 45°C in shaken flasks, when grown in a medium containing 7% wheat bran extract as a carbon source
and 0.5% yeast extract as a nitrogen source. The enzyme has been purified to homogeneity by ultrafiltration, ethanol precipitation,
DEAE cellulose and Sephacryl S-300 chromatography with a 124-fold increase in specific activity and 29.5% recovery. The molecular
weight of the enzyme is 371.5 kDa by gel filtration on Sephacryl S-300 and 87.1 kDa by SDS-polyacrylamide gel electrophoresis.
The enzyme has an optimum temperature of 65°C and an optimum pH of 5.0. Humicola α-galactosidase is a glycoprotein with 8.3% carbohydrate content and is acidic in nature with a pI of 4.0. The K
m
S for p-nitrophenyl-α-D-galactopyranoside, O-nitrophenyl-α-D-galactopyranoside, raffinose and stachyose are 0.279, 0.40, 1.45 and 1.42 mM respectively. The enzyme activity was strongly
inhibited by Ag+ and Hg2+. D-Galactose inhibited α-galactosidase competitively and the inhibition constant (K
i) for galactose was 11 mM.
Received 28 January 1999/ Accepted in revised form 07 April 1999 相似文献