Abstract
An enzyme which catalyzes a decomposition of α-aminoisobutyrate (AIB) was purified and its kinetic properties were investigated. Michaelis constants for AIB decomposing reaction are able to be calculated by Ping Pong initial velocity equation. This enzyme catalyzes also L-alanine: α-ketobutyrate transamination as well as AIB decomposing reaction. Approximately equal values of Michaelis constants were obtained for α-ketobutyrate and pyridoxal 5'-phosphate (PLP), which are common substrates of both reactions.
In higher concentration of the enzyme, transamination between PLP and AIB or L-alanine was detected, whereas the reaction between pyridoxamine 5'-phosphate and pyruvate was not observed. These results are probably ascribed to a difference in affinity of two coenzymes for the enzyme.
