Applying Proteolytic Enzymes on Soybean

Abstract

An indole derivative having blue fluorescence was produced in cooked soybean digest-ed at 37°C for 24 hr with an acid proteinase Molsin (optimum pH: 2.8) from Aspergillus saitoi or a usual acid proteinase pepsin (optimum pH: 1.6) from beef stomach. This in-dole derivative was identical with a condensation product from L-tryptophan and n-hexa-nal. Based on MS, NMR, IR and UV spectrometry, the condensation product was identified as 1-pentyl-2, 3, 4, 9-tetrahydro-lH-pyrido [3, 4-b]-indole-3-carboxylic acid [trivial name: 1-pentyl-1, 2, 3, 4-tetrahydro-2-carboline carboxylic acid-(3)]. Data were presented of the formation of the above indole derivative and of the re-sulting consumption of L-tryptophan and n-hexanal. The possible ocurrence of the formation of Harmala alkaloids, i.e. 2-carboline deriva-tives, through in vitro digestion of soybean with acid proteinases was discussed. A carbonyl-trapping ability of L-tryptophan was suggested.