Human tissue carnosinase (EC 3.4.13.3) had optimum activity at pH 9.5 and was a cysteine peptidase, being activated by dithiothreitol and inhibited by p-hydroxymercuribenzoate. By optimizing assay conditions, the activity per g of tissue was increased 10-fold compared with values in the literature. The enzyme was present in every human tissue assayed and was entirely different from serum carnosinase. Highly purified tissue carnosinase had a broader specificity than hog kidney carnosinase. Although tissue carnosinase was very strongly inhibited by bestatin, it did not hydrolyse tripeptides, and thus appears to be a dipeptidase rather than an aminopeptidase. It had a relative molecular mass of 90 000, an isoelectric point of 5.6, and a K(m) value of 10 mM-carnosine. Two forms of kidney and brain carnosinase were separated by high-resolution anion-exchange chromatography, although only one form was detected by various electrophoretic methods. Homocarnosinase and Mn2+-independent carnosinase were not detected in human tissues, although these enzymes are present in rat and hog kidney.
CITATION STYLE
Lenney, J. F., Peppers, S. C., Kucera-Orallo, C. M., & George, R. P. (1985). Characterization of human tissue carnosinase. Biochemical Journal, 228(3), 653–660. https://doi.org/10.1042/bj2280653
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