An inhibitor I-1, capable of acting on both alpha-amylase and trypsin, was purified to homogeneity from ragi (finger-millet) grains. The factor was found to be stable to heat treatment at 100 degrees C for 1 h in the presence of NaCl and also was stable over the wide pH range 1-10. Pepsin and Pronase treatment of inhibitor I-1 resulted in gradual loss of both the inhibitory activities. Formation of trypsin-inhibitor I-1 complex, amylase-inhibitor I-1 complex and trypsin-inhibitor I-1-amylase trimer complex was demonstrated by chromatography on a Bio-Gel P-200 column. This indicated that the inhibitor is 'double-headed' in nature. The inhibitor was retained on a trypsin-Sepharose 4B column at pH 7.0. Elution at acidic pH resulted in almost complete recovery of amylase-inhibitory and trypsin-inhibitory activities. alpha-Amylase was retained on a trypsin-Sepharose column to which inhibitor I-1 was bound, but not on trypsin-Sepharose alone. Modification of amino groups of the inhibitor with 2,4,6-trinitrobenzenesulphonic acid resulted in complete loss of amylase-inhibitory activity but only 40% loss in antitryptic activity. Modification of arginine residues by cyclohexane-1,2-dione led to 85% loss of antitryptic activity after 5 h, but no effect on amylase-inhibitory activity. The results show that a single bifunctional protein factor is responsible for both amylase-inhibitory and trypsin-inhibitory activities with two different reactive sites.

A field experiment was conducted for 2 years during 1991–93 at the Central Institute of Medicinal and Aromatic plants, Bangalore, India to study the effect of plant spacings (60 × 60, 60 × 45, 60 × 30 and 45 × 45 cm) and nitrogen levels (0, 50, 100 and 150 kg N ha−1 year−1) on growth, herb and oil yield of lemongrass. A closer plant spacing of 45 × 45 cm resulted in higher herb and oil yields compared to wider spacing of 60 × 60 cm. Application of 150 kg N ha−1 year−1 resulted in higher herb and oil yields. Higher nitrogen applications also increased the plant height and number of tillers per clump. The oil content and quality‐was not influenced by spacing and nitrogen levels.

A trypsin/a-amylase inhibitor (TAI) and a chymotrypsin/trypsin inhibitor (CTI) were isolated in homogeneous forms from ragi grains by affinity chromatography using immobilised chymotrypsin and immobilised trypsin. Both the inhibitors were capable of inhibiting the caseinolytic and amidolytic activities of bovine trypsin whereas the esterolytic activity of the enzyme was only weakly affected. While TAI had no action on chymotrypsin, the CTI exerted an inhibitory effect on the caseinolytic activities of bovine a-, p-, y-and 8-chymotrypsins. Both the inhibitors could inactivate the proteolytic actions of bovine as well as human crude pancreatic preparations. TAI showed inhibitory activity against human pancreatic, porcine pancreatic and human salivary amylase in the ratio of 6.5: 5 : I . The possible practical application of TAI for the purification of a-amylases by affinity chromatography is indicated based on the demonstration of the dissociation of porcine pancreatic amylase from a 'trypsin-TAI-amylase' trimer complex in the presence of maltose. The antichymotryptic activity of CTI was less stable than its antitryptic activity at high temperature, acidic pH and on treatment with pepsin. Modification of arginine residues by 1,2-cyclohexane dione led to a preferential inactivation of its antitryptic activity. Treatment of CTI with trinitrobenzene sulphonic acid or pronase, however, caused almost identical loss of both antitryptic and antichymotryptic activities. The mode of inhibition of CTI was non-competitive for trypsin but was uncompetitive for chymotrypsin. The CTI could bind to immobilised trypsin or chymotrypsin but not to irnmobilised TPCK-chymotrypsin or chymotrypsinogen.

No abstract

Lemongrass (Cymbopogon flexuosus (Steud.) Wats) is a perennial, multicut aromatic grass, which yields an essential oil used in perfumery and pharmaceutical industries and Vitamin A, has a long initial lag phase. To utilize the crop growth resources more efficiently during this phase, studies were made to explore the possibility of intercropping food legumes with lemongrass. An experiment conducted during 1992-93 revealed that the food legumes like blackgram (Viyna mungo (L) Hepper), cowpea {Vigna unguiculata (L) Walp) or soybean (Glycine max (L) Merr.) could be intercropped in the initial stages of lemongrass to get extra yields over and above that of lemongrass, without affecting the yield of lemongrass.