Catalyzes the cleavage of 5-oxoproline to form L-glutamate coupled to the hydrolysis of ATP to ADP and inorganic phosphate (PubMed:28830929). In addition, is a potent inhibitor of the autophosphorylation reaction of kinase A (kinA) and its reverse reaction, but does not inhibit phosphate transfer to the Spo0F response regulator once kinase A is phosphorylated. Is an inhibitor of the catalytic domain of kinase A affecting the ATP/ADP reactions and not the phosphotransferase functions of this domain. The inhibition is non-competitive with respect to ATP (PubMed:9334321). 5-oxo-L-proline + ATP + 2 H2O = ADP + H(+) + L-glutamate + phosphate Forms a complex composed of PxpA, PxpB and PxpC (PubMed:28830929). Interacts with PxpC (KipA) (PubMed:9334321, PubMed:21050859, PubMed:28830929). Interaction with PxpC prevents the inhibitory action of PxpB (KipI) (PubMed:9334321, PubMed:21050859). Interacts with KinA. Two PxpB monomers bind via their C-domains at a conserved proline in the KinA dimerization and histidine-phosphotransfer (DHp) domain (PubMed:18823995). Induced by glucose when readily available sources of nitrogen, such as ammonia or glutamine, are scarce. Transcriptionally activated by TnrA and repressed by KipR. Deletion of the gene enhances sporulation (PubMed:9334321). Deletion mutant grows less well than wild type on minimal medium with ammonium as nitrogen source and cannot grow on 5-oxoproline. Mutant lacks 5-oxoprolinase activity and accumulates 5-oxo-L-proline (PubMed:28830929). Belongs to the PxpB family. Was originally (PubMed:8574415 and PubMed:8969502) thought to be a longer ORF that encodes what is now known to be pxpB (kipI) and pxpC (kipA).