Proteinase inhibitory activity of sorghum (Sorghum bicolor ( L ) Moench) varieties was determined. Inhibitory activities in buffer extracts of the millets varied widely. Chymotrypsin inhibitory activity was more pronounced than trypsin inhibitory activity in all sorghum varieties tested. On germination both trypsin and chymotrypsin inhibitory activities were markedly reduced.
Grain sorghum (Sorghum bicolor (L) Moench) is India's most important food crop next to rice and wheat. Sorghum has a large potential for its use in the fermentation industry, in puffed products and in weaning foods for the children of developing countries. The nutrient composition of sorghum indicates that it is a good source of energy, protein, vitamins and minerals including trace elements (Deosthale and Belavady 1978). The proteinase inhibitors in sorghum have been isolated, purified and characterised by Harishkumar et a1 (1978Harishkumar et a1 ( , 1979)). Sorghum also contains tannins, phytic acid and fibre as antinutritional factors (Salunkhe 1982). Little is known about the screening of proteinase inhibitors in sorghum. We have therefore undertaken to study the distribution, and changes during germination, of proteinase inhibitors of sorghum.
The sorghum seeds were obtained from the Agricultural Research Stations at Gulbarga and Dharwad. Other cereals were obtained from a local market. Trypsin and chymotrypsin from bovine pancreas were purchased from Sigma Chemical Co, St Louis, MO, USA. Casein was purchased from Wilson Lab, Bombay. Other reagents were of analytical grade.
Acetone-defatted sorghum meal was prepared from sorghum varieties by soaking the seeds in distilled water at 5ยฐC for 24 h and homogenising with acetone in a blender. The homogenate was filtered under suction with acetone on the filter paper and rapidly air dried. The dry sorghum meal was stirred with 30 ml of 0.1 M phosphate buffer, pH 7.6, for 4 h. It was then centrifuged at 10000 x g for 20 min at 4ยฐC. The supernatant obtained was dialysed against 0.05 M phosphate buffer, pH 7.6. This dialysed extract was used for the proteinase inhibitory assay. The assay was carried out by the casein digestion method (Sumathi and Pattabiraman 1977).