Abstract
Two distinct Ca 2+-activated proteinases were purified and characterized from hearts of hypertensive rats. Ca 2+-activated proteinases I and II, having low and high Ca 2+ requirements, respectively, were first separated by DEAE-cellulose chromatography. The enzymes were then purified individually by different column procedures: chromatography on phenyl-Sepharose, then Sephadex G-200 for proteinase I and reactive-red agarose for proteinase II. The apparent molecular weight of purified proteinase I was 125 000 and that for purified proteinase II was 110 000. Both enzymes are heterodimers made up of a larger catalytic subunit and a smaller subunit devoid of proteinase activity. Ca 2+ concentrations for half-maximal activation were 5 μM for proteinase I and 200 μM for proteinase II. Both enzymes were inhibited by sulfhydryl-modifying agents, but exhibited different characteristics in the auto-digestion reaction in the presence of Ca 2+. Proteinases I and II were also purified from hearts of normotensive rats and shown to be identical to their respective counterparts from hearts of hypertensive rats. However, proteinase II activity in hypertensive rat hearts was significantly elevated as compared to controls.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular Enzymology
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