Abstract
An enzyme useful for preparing semisynthetic polymyxins was found to be produced by a Pseudomonas sp. strain, M-6-3 (closely related to Ps. acidovorans). This enzyme, tentatively named polymyxin acylase, is the first enzyme known which can remove the acyl moiety from an acyl peptide without affecting the peptide moiety. It can be produced in a cell-bound form in excellent yield in a medium containing citric acid as the sole source of carbon. The activity of the acetonedried cell powder of the bacterium was optimum at pH 7.5 and remained stable up to about 50°C for 30min. The apparent Vmax and Km values for colistin (polymyxin E) were 8.7 nmol/min/mg and 2.8mM, respectively. The suspension of the cell-bound enzyme in colistin solution gave a good yield of deacyl colistin and fatty acid(s), and no chemical change occurred in the peptide moiety during the enzyme reaction. This enzyme deacylated not only polymyxins B, M, and P, but also several other fatty acyl peptides. It should be valuable as a tool for the deacylation of various acyl peptides.
