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Asian Journal of Applied Sciences

Year: 2011 | Volume: 4 | Issue: 7 | Page No.: 702-711
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Authors

Mona Al-Onazi

Sooad Al-Dahain

Afaf El-Ansary

Najat Marraiki

Keywords

Research Article

Isolation and Characterization of Thielaviopsis paradoxa L-alanine Dehydrogenase

Mona Al-Onazi, Sooad Al-Dahain, Afaf El-Ansary and Najat Marraiki
Alanine dehydrogenase has not yet been purified from any fungal sources. The aims of this study was to isolate alanine dehydrogenase from Thielaviopsis paradoxa. The biochemical kinetic properties of the enzyme like Km, Vmax, optimum Temperature and pH were also determined. In this study, effect of certain inhibitors on the enzyme was tested. Alanine dehydrogenase (EC 1.4.1.1), an enzyme that catalyzes the reversible deamination of L-alanine in the presence of NAD+, was extracted and characterized from Thielaviopsis paradoxa, a pathogenic fungi for the date palm (Phoenix dactylifera). The enzyme showed maximal activity at pH 9.5 for the deamination of L-alanine and at pH 8.5 for the amination of pyruvate. It was active in the presence of both NAD+ and NADP+ as coenzymes for the deamination of L-alanine. In addition, the enzyme was not absolutely specific to L-alanine as a substrate in the deamination of L-alanine. L-alanine dehydrogenase had Km value for L-alanine (1.35 mM), for NAD+ 0.274 mM, NADH (0.197 mM), pyruvate (8.16 mM) and ammonia (33.5 mM). It was inhibited by Zn2+, CO2+ and by iodoacetate. Activation by using reduced glutathione and DTT are suggestive of sulfhydryl group participation in enzyme activity.
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