초록
<P><SMALL>L</SMALL>-6-Hydroxynorleucine was synthesized from 2-keto-6-hydroxyhexanoic acid using branched-chain aminotransferase from <I>Escherichia coli</I> with <SMALL>L</SMALL>-glutamate as an amino donor. Since the branched-chain aminotransferase was severely inhibited by 2-ketoglutarate, the branched-chain aminotransferase reaction was coupled with aspartate aminotransferase and pyruvate decarboxylase. Aspartate aminotransferase converted the inhibitory 2-ketoglutarate back to <SMALL>L</SMALL>-glutamate by using <SMALL>L</SMALL>-aspartate as an amino donor. On the other hand, pyruvate decarboxylase further shifted the reaction equilibrium towards <SMALL>L</SMALL>-6-hydroxynorleucine through decarboxylation of pyruvate to acetaldehyde. The concerted action of the three enzymes significantly enhanced the yield compared to that of branched-chain aminotransferase alone. In the coupled reaction, 90.2 mM <SMALL>L</SMALL>-6-hydroxynorleucine (> 99% <I>ee</I>) was produced from 100 mM 2-keto-6-hydroxyhexanoic acid, whereas in a single branched-chain aminotransferase reaction only 22.5 mM <SMALL>L</SMALL>-6-hydroxynorleucine (> 99% <I>ee</I>) was produced.</P>