Isolation and properties of a new glutamine transaminase from rat kidney.

A glutamine transaminase has been purified from the soluble portion of rat kidney homogenate; this enzyme, designated as kidney glutamine transaminase K, has different catalytic and physical properties from those previously found for the purified soluble glutamine transaminase of rat liver (liver glutamine transaminase L). Liver glutamine transaminase L is highly active toward methionine, glyoxylate, pyruvate, and several other substrates; kidney glutamine transaminase K is very active toward methionine, phenylalanine, tyrosine, and the cr-keto acid analogs of these amino acids and exhibits relatively little activity toward glyoxylate and pyruvate. Evidence was obtained that the K and L forms of glutamine transaminase are both present in liver and kidney. In addition, both forms of these enzymes are present in these tissues as mitochondrial as well as soluble isozymes. There are therefore at least four separate glutamine-cu-keto acid transaminases in liver as well as kidney. Rat liver w-amidase also occurs in both soluble and mitochondrial isozymic forms.