Further studies on proteinases and alpha 2-macroglobulin activity in diabetic plasma.
Loss of chymotrypsin binding capacity of alpha 2-macroglobulin in diabetic plasma on in vitro incubation, could be partially prevented by phenylmethyl sulphonyl fluoride and pepstatin A. Prior ten-fold dilution of plasma with 0.02 M phosphate buffer (pH 7.0) completely arrested the process. The phenomenon could not be reactivated by Ca2+, lecithin or bovine serum albumin. Diabetic plasma, like normal plasma, exhibited maximal hydrolytic activities on H-D-Pro-Phe-Arg-p-nitroanilide, H-D-Val-Leu-Arg-p-nitroanilide and H-D-Ile-Pro-Arg-p-nitroanilide. The hydrolytic activities were not significantly diminished on incubation of plasma at 37 degrees C for 12 hr, unlike alpha 2-macroglobulin activity. On gel chromatography on Sephadex G-200, part of the proteolytic activity in diabetic plasma coeluted with alpha 2-macroglobulin in the VO region. A second activity peak (absent in normal plasma) was eluted with a Ve/V0 value of 1.40. Possible role of free proteinases in diabetic plasma in the inactivation of alpha 2-macroglobulin is discussed.
Roche
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Department of Biochemistry, Kasturba Medical College, Manipal, Karnataka, India.
Pattabiraman
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TN
D000595:Amino Acid Sequence; D002918:Chymotrypsin / Q000378:metabolism; D003920:Diabetes Mellitus / Q000097:blood / Q000378:metabolism*; D010450:Endopeptidases / Q000097:blood*; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides; D011480:Protease Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D000511:alpha-Macroglobulins / Q000378:metabolism*
D009842:Oligopeptides; D011480:Protease Inhibitors; D000511:alpha-Macroglobulins; D010450:Endopeptidases; D002918:Chymotrypsin