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L‐Asparaginase activity in Leptosphaeria michotii. Isolation and properties of two forms of the enzyme
Author(s) -
JerebzoffQuintin Simonne,
Jerebzoff Stéphan
Publication year - 1985
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1985.tb01215.x
Subject(s) - asparaginase , isoelectric point , enzyme assay , enzyme , specific activity , biochemistry , isoelectric focusing , polyacrylamide gel electrophoresis , asparagine , chromatography , chemistry , ammonium sulfate , gel electrophoresis , hydrolysis , biology , genetics , lymphoblastic leukemia , leukemia
The properties of L‐asparaginase (EC 3.5.1.1) in Leptosphaeria michotii (West) Sacc., which has previously been shown to have an activity rhythm, were analyzed. Two forms of L‐asparaginase were isolated from acetic acid and ammonium sulfate fractionations followed by DEAE‐Sephacel chromatography. The activity of L‐asparaginase changed rhythmically with the same period as that of crude extracts, but the rhythms of the two enzyme forms were out of phase. The two asparaginase forms differed in their isoelectric points and the substrate concentrations for attaining half‐maximal velocity; non‐Michaelis‐Menten kinetics for hydrolysis of L‐asparagine were observed. Analyses of asparaginase form II by polyacrylamide gel electrophoresis showed that four proteins, irrespective of the phase of the activity rhythm at which the enzyme was extracted, could be detected: asparaginase oligomer (M r 130 000 to 140 000), its dimer, an aggregate (M r 500 000 to 600 000) having a low asparaginase activity, and a protein (M r 60 000) without asparaginase activity; the same proteins were found in asparaginase form I. These results indicate that L. michotii asparaginase could be implicated in a protein complex.