Crystal structures and biochemical analyses of the bacterial arginine dihydrolase ArgZ suggests a "bond rotation" catalytic mechanism.

ABSTRACT: A recently discovered ornithine-ammonia cycle (OAC) serves as a conduit in the nitrogen storage and remobilization machinery in cyanobacteria. The OAC involves an arginine catabolic reaction catalyzed by the arginine dihydrolase ArgZ whose catalytic mechanism is unknown. Here we determined the crystal structures at 1.2-3.0 Å of unliganded ArgZ from the cyanobacterium Synechocystis sp. PCC6803 and of ArgZ complexed with its substrate arginine, a covalently linked reaction intermediate, or the reaction product ornithine. The structures reveal that a key residue, Asn⁷¹, in the ArgZ active center functions as the determinant distinguishing ArgZ from other members of the guanidino group-modifying enzyme superfamily. The structures, along with biochemical evidence from enzymati

SUBMITTER: Zhuang N 

PROVIDER: S-EPMC7029115 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature