EFFECT OF ANTIBIOTICS ON RAT-KIDNEY KYNURENINE AMINOTRANSFERASE ACTIVITY

The effects of 26 antibiotics on the activity of rat kidney kynurenine aminotransferase were examined. Among the antibiotics tested, only d-cycloserine and novobiocin showed an inhibiting property on the enzymatic transamination of l-kynurenine and l-3-hydroxykynurenine. Kinetic studies showed that the type of inhibition is noncompetitive in both cases. The inhibition constants (Ki) of d-cycloserine with l-kynurenine and l-3-hydroxykynurenine as substrates are 0.25 mM and 0.35 mM respectively, whereas for novobiocin they are 1.29 mM and 1.44 mM respectively. The Ki values show that d-cycloserine is a potent in vitro inhibitor of kynurenine aminotransferase at concentrations similar to those reached in vivo in human blood during administration of the drug in therapy. © 1979.