Metabolism of basic amino acids in Pseudomonas putida. Intermediates in L-arginine catabolism.

y-Guanidinobutyrate amidinohydrolase, the third enzyme of L-arginine catabolism in Pseudomonas putida, has been purified 6%fold from extracts of cultures grown on L-arginine. Synthesis of the amidinohydrolase is induced by growth on L-arginine or y-guanidinobutyrate, but not by growth on y-aminobutyrate or on urea plus DL-malate. Hydrolysis of y-guanidinobutyrate to y-aminobutyrate and urea proceeds essentially to completion at pH 7 to 11. The purified enzyme specifically requires Mn2+ and exhibits optimum activity at about pH 10 and 50”. The K,,, for yguanidinobutyrate is 32 mM at pH 10. While 6-guanidinovalerate and e-guanidinocaproate also are hydrolyzed, the value of both K, (6-guanidinovalerate = 206 mM; e-guanidinocaproate = 163 mM) and of Vma, (606, 27, and 11 e.u. per mg for y-guanidinobutyrate, &guanidinovalerate, and e-guanidinocaproate, respectively) suggest that y-guanidinobutyrate is the natural substrate. The molecular weight of the purified enzyme was estimated to be 178,000 by gel permeation chromatography and 190,000 by sucrose density gradient centrifugation.