A mycothiol (MSH, N-acetylcysteinyl-glucosaminyl-inositol) S-conjugate amidase, it recycles conjugated MSH to the N-acetyl cysteine conjugate (AcCys S-conjugate, a mercapturic acid) and the MSH precursor. Involved in MSH-dependent detoxification of a number of alkylating agents and antibiotics. H2O + mycothiol S-conjugate = 1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside + an N-acetyl-L-cysteine-S-conjugate Binds 1 zinc ion per subunit. Monomer. Transiently induced by thiol-oxidant diamide, under direct control of SigR. Also induced when MSH is oxidized or conjugated. Loss of amidase activity on mycothiol bimane, leading to dramatically decreased levels of N-acetylcysteinyl bimane. Increased sensitivity to a number of alkylating agents and antibiotics including N-ethylmaleimide and lincomycin. Belongs to the MshB deacetylase family. Mca subfamily.