Slowly hydrolyzes 6-aminopenicillinic acid and 7-aminocephalosporanic acid (ACA) derivatives. May be involved in the synthesis of the cell wall peptidoglycan. a beta-lactam + H2O = a substituted beta-amino acid Inhibited by cloxacillin and oxacillin but not by ACA derivatives or metal chelators. kcat is 1.06 min(-1) with ampicillin as substrate. kcat is 0.74 min(-1) with benzylpenicillin as substrate. kcat is 0.55 min(-1) with amoxicillin as substrate. kcat is 0.30 min(-1) with cephaloridine as substrate. kcat is 0.28 min(-1) with nitrocefine as substrate. Monomer. Antibodies against HcpA are present in sera from human patients infected by Helicobacter pylori. Belongs to the hcp beta-lactamase family.