Abstract. The latex of Synadenium grantii was found to contain esterolytic activity. Polyacrylamide gel electrophoretic study coupled with substrate and inhibitor specificity studies revealed the presence of multiple forms of carboxylesterases and cholinesterases in the latex. One of the carboxylesterases of the latex was purified by acetone fractionation, carboxymethyl-Sephadex chromatography and Sepharose-6B gel filtration. The homogeneity of the enzyme was established by polyacrylamide gel electrophoresis, isoelectric focussing and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The enzyme consists of a single polypeptide chain with a molecular weight of 14,000. The amino acid analysis of the purified enzyme revealed that it contained a greater number of neutral and acidic, compared to basic amino acid residues. The isoelectric pH of the enzyme was found to be 4·0. The enzyme was a glycoprotein as revealed by periodic acid Schiff-staining technique. Studies with different organophosphate and carbamate inhibitors showed that this enzyme was sensitive to organophosphates. The product inhibition studies with this enzyme showed linear competitive inhibition with acetate and linear non-competitive inhibition with 1-naphthol.

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Different varieties of finger millet (Eleusine coracana Gaertn.) were screened for esterase activity colorimetrically and electrophoretically using 1-naphthyl acetate and acetylthiocholine chloride as substrates. The Indian brown seed coat variety (Purna), the Indian white seed coat variety (Hamsa), hybrids of these designated as HPB (brown) and HPW (white), African varieties (brown) and Indian-African hybrid varieties (brown) all exhibited 1-naphthyl acetate hydrolysing activity and showed 6,5,6,5,8 and 8 esterolytic bands respectively on gel electrophoresis. The white seed coat varieties, both parental (Hamsa) and hybrid (HPW), did not possess any acetylthiocholine chloride hydrolysing activity while all the brown seed coat varieties did, the African varieties having greater activities than Indian brown seed coat varieties. Thus, the demonstrable variation in esterase isozymic pattern and cholinester hydrolysing activity with the varieties tested provides a useful genetic marker for identifying different varieties of finger millet.