Intermediates and enzymes between alpha-ketoarginine and gamma-guanidinobutyrate in the L-arginine catabolic pathway of Pseudomonas putida

Abstract

In Pseudomonas putida P2 grown on L-arginine as the sole source of carbon and nitrogen, catabolism of L-arginine forms of alpha-ketoarginine, gamma-guanidinobutyrate, and gamma-aminobutyrate. A previously undetected intermediate, gamma-guanidinobutyraldehyde, is identified as the product of alpha-ketoarginine decarboxylase. An 86-fold purification of this enzyme is described. Activity is thiamine pyrophosphate-dependent and cofactor reassociation is facilitated by divalent cations. The order of effectiveness is Mn-2+ greater than Mg-2+, Co-2+ greater than Ca-2+ greater than Ni-2+ greater than Zn-2+. An inducible enzyme that catalyzes conversion of gamma-guanidinobutyraldehyde to gamma-guanidinobutyrate has been studied in cell-free extracts. NAD-+, but no other cofactors, is required. By differential nutritional growth experiments, 4 regulatory units for the L-arginine pathway are proposed and inducers of 2 units are identified.