Galactomannan content and key enzymes of its metabolism in seedsof cluster bean [Cyamopsis tetragonoloba (L.) Taub.]

Abstract

The present investigation was carried out to estimate galactomannan content in mature seeds of 17 guar genotypes and activity of enzymes involved in galactomannan metabolism. Galactomannan content was found in the range of 16.82 (in IC 310630) to 36.68 per cent (in HG 3-2). The developing pods were sampled at 25, 32, 39 and 46 days after flowering (DAF) for a-galactosyltransferase, ß-D-mannosidase & ß-1, 4-mannanase assay. The mean a-galactosyltransferase specific activity increased from 25 to 39 DAF (1557 to 3093 units) followed by decrease at 46 DAF (1484 units). The mean specific activity increased from 392 to 3166 units with the increase in galactomannan content from 16.82 to 36.68 per cent. Thus, this enzyme showed highly positive correlation with the galactomannan content. The mean specific activity of ß-D-mannosidase increased gradually from 25 to 39 DAF (67 to 138 units) followed by sharp decrease at 46 DAF (32 units). The mean specific activity of ß-1, 4-mannanase was found maximum at 25 DAF (102 units) and afterwards, it decreased continuously with advancement of days after flowering up to 46 days (9 units). On the whole, it can be said that the ß-D-mannosidase requires prior activity of ß-1, 4-mannanase for galactomannan catabolism while a-galactosyltransferase activity is positively correlated with galactomannan content and play a major role in guar gum synthesis and can be further used for gum improvement via genetic manipulation.