Mechanism
This hydrolase converts CS2 into H2S. The process is similar to the hydration of CO2 by carbonic anhydrase. This similarity points to a likely mechanism. The zinc at the active site is tetrahedral, being coordinated by Cys 35, His 88, Cys 91 and water. The water is deprotonated to give a zinc hydroxide that adds the substrate to give a Zn-O-C(S)SH intermediate. A similar process is proposed to convert COS into . :CS2 + H2O → COS + H2S :COS + H2O → CO2 + H2S The apoenzyme form, lacking the zinc cofactor, has a molecular weight of 382815.4 g/mol. The chloride ion and the 3,6,9,12,15,18,21,24,27,30,33,36,39-tridecaoxahentetracontane-1,41-diol (C28H58O15) are the two main ligands seen on the enzyme in this form. There are 16 polymer chains seen in this form contributing to the heaviness of the enzyme. This form is also sometimes termed the selenomethionine form. ==References==