Activation studies of the beta-carbonic anhydrases fromEscherichia coliwith amino acids and amines

A beta-carbonic anhydrase (CA, EC 4.2.1.1) from the widespread bacteriumEscherichia coli(EcoCA beta), encoded by the CynT2 gene, has been investigated for its catalytic properties and enzymatic activation by a panel of amino acids and amines. EcoCA beta showed a significant catalytic activity for the hydration of CO(2)to bicarbonate and a proton, with a kinetic constantk(cat)of 5.3 x 10(5)s(-)and a Michaelis-Menten constantK(M)of 12.9 mM. The most effective EcoCA beta activators were L- and D-DOPA, L-Tyr, 4-amino-Phe, serotonin and L-adrenaline, withK(A)s from 2.76 to 10.7 mu M. L-His, 2-pyridyl-methylamine, L-Asn and L-Gln were relatively weak activators (K(A)s from 36.0 to 49.5 mu M). D-His, L- and D-Phe, L- and D-Trp, D-Tyr, histamine, dopamine, 2-(aminoethyl)pyridine/piperazine/morpholine, L-Asp, L- and D-Glu haveK(A)s from 11.3 to 23.7 mu M. Endogenous CA activators may play a role in bacterial virulence and colonisation of the host.