Purification, characterization and immunocytochemical localization of mouse kidney carnosinase

Mouse kidney carnosinase (aminoacyl-L-histidine hydrolase, EC 3.4.13.3) has been isolated, the amino acid composition determined and antiserum prepared against it. The apparent subunit molecular weight is 58 000, which increases to 112 000 on crosslinking. Carnosinase is sensitive to chelating agents and is 50% inhibited by 0.3 microM EDTA, 35 microM o-phenanthroline, or 35 microM 8-hydroxyquinoline-5-sulfonic acid. The Km for carnosine is 60 microM. Anserine is a poor substrate and homocarnosine a non-substrate, with Ki values of 37 and 17 microM, respectively. Mn2+ shifts the Km for carnosine to approx. 2 mM and increases the Vmax about 50%. The specific antiserum discriminates between this carnosinase and a second carnosinase activity which is absolutely dependent on Mn2+ for activity (Margolis, F.L., Grillo, M., Brown, C.E., Williams, T.H., Pitcher, R.G. and Elgar, G.J. (1979) Biochim. Biophys. Acta 570, 311-323). Immunocytochemistry with this antiserum has demonstrated carnosinase to be localized in proximal tubules of kidney, glandular cells of uterus and nasal olfactory mucosa and in vomeronasal and certain other nerve pathways.