Studies on the  -Galactosidase Activity of Saccharomyces fragilis

Szabó, Gábor; Davies, R. E.

doi:10.1099/00221287-37-1-99

Cited by 7 publications

(1 citation statement)

References 1 publication

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“…Inhibition of K. fragilis P-galactosidase by PCMB has been reported by others (Szabo and Davies 1964;Wendorff 1969;Chan 1971;Uwajima et al 1972). Little or no inhibition was found with iodoacetate (Davies 1964;Wendorff 1969).…”

Section: Effect Of Sulfhydryl Enzyme Inhibitors On Activitymentioning

confidence: 67%

Stability and Enzymatic Properties of ?-Galactosidase From Kluyveromyces Fragilis

Mahoney

Whitaker

1978

J Food Biochemistry

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Kluyveromyces fragilis β‐galactosidase purified to electrophoretic, chromatographic and immunochemical homogeneity was used. The enzyme specifically required potassium ions for stability; MnCl2 increased the stability. The enzyme was maximally stable at pH 6.5 to 7.5; stability was markedly less at pH's below 6.5 and above pH 8.5 at 37°C. Temperature denaturation followed first order kinetics with an activation energy for denaturation of 56 kcal/mol. Maximum activity was achieved in the presence of 5mM KCl. In potassium phosphate buffer, the enzyme was further activated by Mn2+, Mg2+, Co2+ and Zn2+; Mn2+, at 0.1 mM, gave the highest activation. None of these ions activated the enzyme in Tris buffer and> 0.1 mM Zn2+ caused complete loss of activity. Activity was completely inhibited by ethylenediaminetetraacetate and partially restored by addition of MnCl2. p‐Chloromercuribenzoate caused rapid loss of activity which could be restored by dithiothreitol. Iodoacetamide, N‐ethylmaleimide and sodium tetrathionate did not inactivate the enzyme. The enzyme was specific for β‐galactosides. Km's for o‐nitrophenyl β‐D‐galactopyranoside and lactose were 2.72 and 13.9 mM, respectively, at pH 6.6 D‐Galactono‐1, 4‐lactone was a good competitive inhibitor (Ki=0.17 mM). pH optimum for hydrolysis of o‐nitrophenyl β‐D‐galactopyranoside was 6.2–6.4. Vmax for this substrate was dependent on two ionizable groups of pKa of 6.13 and 6.51 while Vmax/Km was dependent on two ionizable groups of pKa of 6.39 and 7.23. Activation energy for hydrolysis of o‐nitrophenyl β‐D‐galactopyranoside at pH 7.0 was 9.1 kcal/mol in the range 20–40°C.

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Section: Effect Of Sulfhydryl Enzyme Inhibitors On Activitymentioning

confidence: 67%

Stability and Enzymatic Properties of ?-Galactosidase From Kluyveromyces Fragilis

Mahoney

Whitaker

1978

J Food Biochemistry

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Induction of ? galactosidase in the yeast Kluyveromyces lactis

González

Berry

1982

Biotechnol Lett

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Modes of lactose uptake in the yeast species Kluyveromyces marxianus

Carvalho-Silva

Spencer‐Martins

1990

Antonie van Leeuwenhoek

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Twelve lactose-assimilating strains of the yeast species Kluyveromyces marxianus and its varieties marxianus, lactis and bulgaricus were studied with respect to transport mechanisms for lactose, glucose and galactose, fermentation of these sugars and the occurrence of extracellular lactose hydrolysis. The strains fell into three groups. Group I (two strains): Fermentation of lactose, glucose and galactose, extracellular lactose hydrolysis, apparent facilitated diffusion of glucose and galactose; Group II (two strains): Lactose not fermented, glucose and galactose fermented and transported by an apparent proton symport, extracellular hydrolysis of lactose present (one strain) or questionable; Group III (eight strains): Lactose, glucose and galactose fermented, lactose transported by an apparent proton symport mechanism, extracellular hydrolysis of lactose and transport modes for glucose and galactose variable.

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Studies on the -Galactosidase Activity of Saccharomyces fragilis

Cited by 7 publications

References 1 publication

Stability and Enzymatic Properties of ?-Galactosidase From Kluyveromyces Fragilis

Stability and Enzymatic Properties of ?-Galactosidase From Kluyveromyces Fragilis

Induction of ? galactosidase in the yeast Kluyveromyces lactis

Modes of lactose uptake in the yeast species Kluyveromyces marxianus

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