Agmatinase subfamily currently includes metalloenzymes such as agmatinase, guanidinobutyrase, guanidopropionase, formimidoylglutamase and proclavaminate amidinohydrolase. Agmatinase (agmatine ureohydrolase; SpeB; EC=3.5.3.11) is the key enzyme in the synthesis of polyamine putrescine; it catalyzes hydrolysis of agmatine to yield putrescine and urea. This enzyme has been found in bacteria, archaea and eukaryotes, requiring divalent Mn and sometimes Zn, Co or Ca for activity. In mammals, the highest level of agmatinase mRNA was found in liver and kidney. However, catabolism of agmatine via agmatinase apparently is a not major path; it is mostly catabolized via diamine oxidase. Agmatinase has been shown to be down-regulated in tumor renal cells. Guanidinobutyrase (Gbh, EC=3.5.3.7) catalyzes hydrolysis of 4-guanidinobutanoate to yield 4-aminobutanoate and urea in arginine degradation pathway. Activity has been shown for purified enzyme from Arthrobacter sp. KUJ 8602. Additionally, guanidinobutyrase is able to hydrolyze D-arginine, 3-guanidinopropionate, 5-guanidinovaleriate and L-arginine with much less affinity, having divalent Zn ions for catalysis. Proclavaminate amidinohydrolase (Pah, EC 3.5.3.22) hydrolyzes amidinoproclavaminate to yield proclavaminate and urea in clavulanic acid biosynthesis. Activity has been shown for purified enzyme from Streptomyces clavuligerus. Clavulanic acid is the effective inhibitor of beta-lactamases. This acid is used in combination with the penicillin amoxicillin to prevent antibiotic's beta-lactam rings from hydrolysis, thus keeping the antibiotics biologically active.
Jiyao W et al.(2023). "The conserved domain database in 2023.",