title: Sorghum proteinase inhibitors. 2. Mode of interaction with serine proteinases.
abstract: Investigations have been carried out on the complex formed between sorghum Inhibitor III and alpha-chymotrypsin by physico-chemical methods. An apparent dissociation constant (Ki) of 4.0 X 10(-8) M has been calculated for the complex. This enzyme-inhibitor complex was isolated by gel filtration on Sephadex G-75 and a molecular weight of 48,000 was estimated for the complex. The formation of the complex was accompanied by spectral changes in the 270--300 nm region of the spectrum. Preliminary evidence suggests that the sorghum Inhibitor III is structurally altered when it is incubated with alpha-chymotrypsin. Catalytically inactive derivative of alpha-chymotrypsin and trypsin, as well as their zymogens, did not interfere with the activity of the sorghum inhibitor towards the native enzymes. Sorghum Inhibitor I was shown to be a 'double-headed' inhibitor since it inhibits both trypsin and alpha-chymotrypsin independently.
mesh_terms: D002850:Chromatography, Gel; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D002523:Edible Grain / Q000032:analysis*; D004586:Electrophoresis; D010450:Endopeptidases; D008970:Molecular Weight; D011480:Protease Inhibitors / Q000302:isolation & purification; D013057:Spectrum Analysis; D014357:Trypsin; D014361:Trypsin Inhibitors
chemical_list: D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; D010450:Endopeptidases; D002918:Chymotrypsin; D014357:Trypsin