Gastrointestinal Transit of Soybean Trypsin Inhibitor and Fluctuations in Intraluminal Trypsin

Soybean trypsin inhibitor of Kunitz type (STI) was modified by reduced alkylation with NaBH₄ and HCHO, and examined for resistance to in vitro digestion from the viewpoint of inhibitory activity and immunoreactivity. Methylated STI was exactly alike in that respect. Hence, STI was in part replaced by its [¹⁴C]methyl-labeled specimen and their (17: 3) mixture was used as a proteinous and unabsorbable marker for digestibility experiments. When STI was immunochemically measured in intraluminal leavings in segments of the rat digestive tract, its recovery decreased progressively with the elapse of time. As a result of radioactivity measurement, however, the recovery of [¹⁴C]labeled STI proved almost quantitative all together over a period of 7 h postprandial. Concurrently, gastric emptying and intestinal transit of digesta were assessed in terms of intraluminal STI movement. After moving out from the stomach, STI rapidly passed through the upper small intestine with depression of the trypsin activity, and stayed in the lower small intestine for a few or several hours (all that while, the trypsin activity was not depressed so much). A similar pattern was observed for the intraluminal movement of a food additive ‘indigo carmine’ in another experiment. It was assumed from these observations that digesta would also have gone past the upper small bowel irrespective of ingesting either a powdered 20% casein diet or a dumpling-kneaded artificial bait.     

Trypsin inhibitors in plants

Trypsin inhibitors were found in several food plants. Potato and sweet corn were the most inhibitory, while fruits had negligible activity. Intermediate in activity were sweet potato, spinach, broccoli, Brussels sprouts and cucumber. The trypsin inhibitor of sweet corn was isolated by extraction in dilute salt solution, ammonium sulfate fractionation, chromatography with Sephadex G75 and CM-cellulose and lyophilization. Two components were demonstrated by disc gel electrophoresis. The inhibitor was heat stable. It had little inhibitory activity against papain but was moderately active against chymotrypsin.     

胰蛋白酶的固定化及其性质研究

 以自制的脱乙酰壳多糖作载体,戊二醛为交联剂,对胰蛋白酶的固定化条件及其固定化酶的性质进行了研究。考查了交联剂的用量、pH值、以及载体与酶的比例等因素对胰蛋白酶固定化的影响。在所选择的固定化条件下,固定化酶的活性回收可达50％以上。同时研究了固定化胰蛋白酶的一些性质;最适温度60℃,最适PH8.0,Km值比可溶性酶升高,热稳定性、pH贮存稳定性以及在乙醇水溶液中的稳定性明显高于可溶性胰蛋白酶。在柱式反应器内,以2％酪蛋白为底物对,操作半衰期为40天。     

Trypsin immobilization in silica gel

Trypsin immobilization in an inorganic polymer, i.e. silica gel, was investigated. Properties of the immobilized enzyme were examined. It was found that the enzyme retained its activity, depending on the gel genesis and dehydration of the carrier. The effect of stabilizing supplements on the enzyme activity was studied. The enzyme immobilization was accompanied by an increase in its thermostability.