Abstract: The L-leucine aminotransferase (LAT) from Black locust (R0binia pseudo-acacia L . ) (?)seedlings was purified by heat treatment , ammonium sulfate fractionation, sephadex G-100 and DEAE-cellulose column chromatqgraphy. The data show that final purification obtained was 61 fold. Photographs of polyacrylamide dise gels stained with Coomassie blue R-250 after electrophores is of this LAT preparation showed single band. The MW of the enzyme was 7x 10. The enzyme gave pH optima of 9.0 and temperature optima of 60℃. The Km values to L-lcucine and a-Ketoglutarate were 2.5mM and 3.5mM respectively. The absorption spectrum of the enzyme is typical Of enzymes that contain pyridoxal phosphate with major peaks at 230 and 280nm and smaller coenzyme-specific peaks at 320 and 425nm. Overnight dialysis of this enzyme against 60mM patassium phosphate buffer (ph7.8) (containing 1mM β-mercaptoethanol 1mM EDTA and 5mM L-leucine) essentially removes the coenzyme-specific peaks. The apoenzymc has no detectable activity without added pyridoxal phosphate. However, 80% of the activity of apoenzyme is restored after lh. preincubation period with pyridoxal phosphate, and if a longer period of preincubation is allowed, 100% of the original activity is regained. These results indicate that the cocnzyme of LAT from Black locust seedlings is pyridoxal phosphate. The aminotransferse is inhibited by substrate analogues (dicarboxylic acid) incapable of undergoing transamination. The LAT of Black locust displays sensitivity to carbonyl binding reagents which are typical of pyridoxal phosphate enzyme. Of a number of cationic species tested, only produces an inhibiting effect on activity (10% inhibition), Other cotions found to fexert no effect on the activity include Mg2+, Mn2+, Cu2 + , Hg2 + , Fe3+ , and Al3+. The lack of an effect by I×l0-4 M Hg2 + , as well as by I×l0-3 M EDTA, implies that no sufhydryl group, as well as no involvement of a metal ion.