Cauxin

Cauxin is a peptidase that is excreted in large amounts in cat urine. Cauxine has been shown to hydrolyze 3-methylbutanol-cysteinylglycine (3-MBCG) in the urine into felinine which then slowly degrades into the putative cat pheromone 3-mercapto-3-methylbutan-1-ol (MMB).

Cauxin protein from feline urine was reported in 2008 to act as a nucleator for struvite crystals, in an in vivo system containing magnesium, ammonium, and phosphate ions. Thus, this protein may act as one cause for feline urinary stones.