 The urine of mature male cats in particular contains the amino acid known as felinine which is a precursor to 3-mercapto-3-methylbutan-1-ol (MMB), the sulfur-containing compound that gives cat urine its characteristically strong odor.Felinine is produced in the urine from 3-methylbutanol-cysteinylglycine (3-MBCG) by the excreted peptidase cauxin.It then slowly degrades via bacterial lyase into the more-volatile chemical MMB.