Some Properties of Aspartate and Alanine Aminotransferases from Trichoderma viride

Department of Biochemistry, University of Nigeria, Nsukka, Nigeria ABSTRACT Summary: Aspartate aminotransferase (EC 2.6.1.1 ) and alanine aminotransferase (EC 2.6.1.2 ) were extracted from mycelia of Tricchoderma viride , partially purified and characterized. The pH optima for the enzyme activities were 9.0 and 8.6, respectively. Both enzymes were relatively stable at 37 °C but rapidly denatured at 60 °C. They were inducible by both L -aspartate and DL -alanine, but aspartate was the better inducer. The apparent Michaelis constants for aspartate aminotransferase when L -aspartate and 2-oxoglutarate were used were 7.14 mM and 1.32 mM, respectively. In the case of alanine aminotransferase, using DL -alanine and 2-oxoglutarate the corresponding values were 8.33 mM and 1.85 mM, respectively. The enzymes were competitively inhibited by succinate with K i values of 21 mM and 17 mM for aspartate aminotransferase and alanine aminotransferase, respectively. Both enzymes could use L -methionine whereas only aspartate aminotransferase could use L -tyrosine as amino donor.