Multiple ribonucleases of human urine.

Abstract

Four major urine ribonuclease (RNase) activities, designated bands A-D, were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and activity staining. Bands A, B, and C have alkaline pH optima and display molecular weights of 31 000, 23 000, and 20 000, respectively, upon sodium dodecyl sulfate (NaDodSO4) gel electrophoresis and weights of 44 000, 28 000, 22 000 upon gel filtration. Band D, with a pH optimum slightly below neutrality, has a molecular weight of 16 000 or 15 000, respectively, determined by the above methods. Band A, the most abundant activity in urine, is heterogeneous and resembles serum RNase 1 on electrophoresis and on phosphocellulose and Sephadex chromatography. Band B is similar to a minor, unnamed component of serum RNase activity while band C resembles serum RNase 3. Band D is similar to the leukocyte RNase-like activity of serum [Blank, A., & Dekker, C.A. (1981) Biochemistry (preceding paper in this issue)]. Band A is present in urine at a concentration high than that of RNase 1 in serum. In contrast, urine counterparts of serum RNases 2, 4, and 5 are not apparent upon either phosphocellulose chromatography [see also Yamanaka, M., Akagi, K., Murai, K., Hirao, N., Fujimi, S., & Omae, T. (1977) Clin. Chim. Acta 78, 191-201] or NaDodSO4 get electrophoresis; a urine counterpart of serum RNase 3 can be detected only by the more sensitive electrophoretic method. These results indicate that RNase 2-5 are processed differently by the kidney than RNase 1. After reconciliation of reported differences in their pH optima and molecular weights, five apparently diverse RNase preparations described in the literature can be related to band A activity and three preparations to band D. However, we are unable to confirm a previous report of a human urine enzyme indistinguishable from bovine pancreatic RNase A.