No abstract

No abstract

The presence of trypsin inhibitors is demonstrated in cotyledonary albumins of Vigna unguiculata by cross-electrophoresis against trypsin and by kinetic measurements. These inhibitors are isolated by selective trapping on insoluble trypsin. On the other hand, evidence is given showing that cotyledonary albumins hydrolyse α-N-benzoyl-DL-arginine-p-nitroanilide (BAPA) and casein. Purified trypsin-inhibitors partially inhibit the caseolytic activity of albumins but do not influence their hydrolytic activity toward BAPA. A partial characterisation of proteases and inhibitors is carried out. A model for the regulation of the proteolytic activities of the seeds by trypsin inhibitors is suggested.

The prevalence of primary adult lactose malabsorption and the pattern of milk use were studied among 109 Indians from various tribes of the American Great Basin and Southwest. Included were 100 persons who reported being full-blooded Indians as well as three with Mexican admixture and 6 with some European ancestry. Lactose malabsorption was found in 92% of the full-blooded Indians but in only 50% Indians who acknowledged European admixture. These results agree with those of studies of native Americans done elsewhere which show very high prevalences of such lactose malabsorption among adults reported as fullblooded and lower prevalences among individuals with admitted European ancestors. The suggestion made is that in pre-Colombian times, before interbreeding with Europeans began on any scale, such lactose malabsorption may have been nearly universal among native American adults. Most of the Indians studied consumed abundant milk since childhood but were nevertheless predominantly malabsorbers as adults. This argues against the induction hypothesis advanced by some to explain the striking ethnic differences that occur around the world in primary adult lactose malabsorption.

Cotyledonary cells are submitted to fractionation by isopycnic centrifugation. Small intact protein bodies are collected in the densest zones (d=1.205-1.237 g/cm(3)). Fragments of larger bodies are gathered in zones of lower density (d=1.205 g/cm(3)). Small dense bodies are largely sedimentable after dilution, whereas fragments of the large bodies dissociate into a dense sedimentable clot and into floating elements which contain most of the globulins and all of the albumins. Among the dissociated floating components are the BAPA-active endopeptidases and the trypsin inhibitors (BAPA=α-N-benzoyl-DL-arginine-p-nitroanilide). A caseolytic activity remains with the dense mass. The localisation of the albumins, globulins, proteases and trypsin inhibitors is discussed. Relations between solubility, structure and function are considered.