Abstract
Branched chain amino acid aminotransferase was partially purified from Pseudomonas sp. by ammonium sulfate fractionation, aminohexyl-agarose and Bio-Gel A-0.5m column chromatography.
This enzyme showed different substrate specificity from those of other origins, namely lower reactivity for L-isoleucine and higher reactivity for L-methionine.
Km values at pH 8.0 were calculated to be 0.3mM for L-leucine, 0.3mM for α-ketoglutarate, 1.1mM for α-ketoisocaproate and 3.2mM for L-glutamate.
This enzyme was activated with β-mercaptoethanol, and this activated enzyme had different kinetic properties from unactivated enzyme, namely, Km values at pH 8.0 were calculated to be 1.2mM for L-leucine, 0.3mM for α-ketoglutarate.
Isocaproic acid which is the substrate analog of L-leucine was competitive inhibitor for pyridoxal form of unactivated and activated enzymes, and inhibitor constants were estimated to be 6mM and 14mM, respectively.
