Abstract
d-3-Aminoisobutyrate-pyruvate aminotransferase (EC 2.6.1.40) was purified 1900-fold from rat liver extract. The purified enzyme showed a molecular mass of 180 kDa by gel-permeation HPLC analysis using a TSK gel G3000SW column. Reductive polyacrylamide gel electrophoresis in sodium dodecyl sulfate resulted in identification of a single band of approx. 50 kDa, indicating that the native enzyme is probably a tetrametric protein. The specific activity of the purified enzyme was 1.14 μmol/min per mg protein. d-3-Aminoisobutyrate and β-alanine were good amino donors. The K m value for l-3-aminoisobutyrate was 100-times larger than that for the d-isomer. The apparent K m values for d-3-aminoisobutyrate and β-alanine were 35 and 282 μM, respectively. Pyruvate, glyoxylate, oxalacetate 2-oxo- n-valerate, and 2-oxo- n-butyrate were good amino acceptors. The apparent K m values for pyruvate and glyoxylate were 32 and 44 μM, respectively.
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