Properties of recombinant Staphylococcus haemolyticus cystathionine beta-lyase (metC) and its potential role in the generation of volatile thiols in axillary malodor

Abstract

Enzymes implicated in cysteine and methionine metabolism such as cystathionine beta-lyase (CBL; EC 4.4.1.8), a pyridoxal-5'-phosphate (PLP)-dependent carbon-sulfur lyase, have been shown to play a central role in the generation of sulfur compounds. This work describes the unprecedented cloning and characterization of the metC-cystathionine beta-lyase from the axillary-isolated strain Staphylococcus haemolyticus AX3, in order to determine its activity and its involvement in amino acid biosynthesis, and in the generation of sulfur compounds in human sweat. The gene contains a cysteine/methionine metabolism enzyme pattern, and also a sequence capable to effect beta-elimination. The recombinant enzyme was shown to cleave cystathionine into homocysteine and to convert methionine into methanethiol at low levels. No odor was generated after incubation of the recombinant enzyme with sterile human axillary secretions; sweat components were found to have an inhibitory effect. These results suggest that the generation of sulfur compounds by Staphylococci and the beta-lyase activity in human sweat are mediated by enzymes other than the metC gene or by the concerted activities of more than one enzyme.