Abstract
Esterase activities toward various O-acylthiamines were demonstrated in human erythrocytes stroma and endosoma. The stromal enzyme showed higher activity to acyl radicals of the short chain (OAT, OPT), and was strongly inhibited by DFP and eserine. The endo somal enzymew as active to OBuT and OVT, the derivatives of the middle number of acyl carbon. It was not inhibited by 10^<-5> M eserine, but strongly inhibited by DFP. These activities were supposed to be due to erythrocytes acetylcholinesterase and ali-esterase, respectively. Acyl-TDS that penetrated into the cell sand reduced, was shown to be retained in the form of thiamine on deacylation by the endosomal enzyme. The reduction and deacylation processes were clearly distinguished each other by an inhibition experiment with DFP. The general mechanisms concerning transport phenomena of thiamine derivatives in erythrocytes, were discussed.
