A mycothiol (MSH, N-acetyl-cysteinyl-glucosaminyl-inositol) S-conjugate amidase, it recycles conjugated MSH to the N-acetyl cysteine conjugate and the MSH precursor. Involved in MSH-dependent detoxification of a number of alkylating agents and antibiotics. Activity is specific for the mycothiol moiety. Has a low but measurable deacetylation activity on GlcNAc-Ins (N-acetyl-glucosaminyl-inositol), and thus can also directly contribute to the production of MSH. H2O + mycothiol S-conjugate = 1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside + an N-acetyl-L-cysteine-S-conjugate Binds 1 Zn(2+) ion per subunit. Partially inhibited by MSH when MSmB is used as substrate. Competitively inhibited by the GlcNAc-cyclohexyl derivative 5-(4-chlorophenyl)-N-((2R,3R,4R,5S,6R)-2-(cyclohexylthio)-tetrahydro-4,5-dihydroxy-6-(hydroxymethyl)-2H-pyran-3-yl)furan-2-carboxamide, which also inhibits MshB. at 50 mM HEPES, pH 7.5, 37 degrees Celsius, 50 mM NaCl. Monomer. MSH is a glutathione analog and is essential for this organism. As MSH does not exist in its host (human) enzymes that are required for its metabolism (such as this one) are potential therapeutic targets. Belongs to the MshB deacetylase family. Mca subfamily.