A gamma-glutamyltranspeptidase (GGT, E.C. 2.3.2.2) was isolated from a strain (A8) originating from Lake Bogoria (Kenya) and homologous with Bacillus pumilus. This GGT shows an optimal activity at pH 8.9 and 62 degrees C. The enzyme is thermostable up to 43 degrees C. The best reagent among the potential inhibitors was shown to be DON, which is an inhibitor highly specific for GGTs. Gly-Gly-Ala, Gly-Gly-Gly and Gly-Gly were identified as the best acceptors for the transpeptidation reactions catalyzed by the enzyme. The SDS-PAGE study revealed that the enzyme consists of two non-identical subunits (38,000 and 23,000). Only the large subunit was active when the enzyme was dissociated under denaturing conditions. The behavior of the native enzyme suggests that the active site of the large subunit is masked by the small subunit.

No abstract

No abstract

This study sought to define what attributes of sweetpotatoes are most critical to textural qualities of their fried chips for effective selection of specialty cultivars. It compared texture-predicting fracturability of fried chips prepared from either structurally intact or disrupted slices of 13 cultivars; analyzed major attributes of these sweetpotatoes, including starch contents and properties, dry matter contents, and structure-related penetration resistances (measured using an adapted penetration test); and evaluated correlational relationships between these attributes of sweetpotatoes and fracturability of fried chips. The study found that lower dry matter (<22.6% F.W.) and starch contents (<10% F.W.), and lower gelatinization temperatures of starch in sweetpotatoes generally resulted in a more favorable fracturability (lower peak break force) of fried chips. However, contrary to potato, total dry matter content is not the sole determinant of textural qualities of fried sweetpotato chips; instead, structurerelated attributes of sweetpotatoes appear to have a greater impact. Partial structural disruptions of sweetpotato slices by blanching effectively improved fracturability of fried chips in all analyzed cultivars, and by ~40% in eight of the 13 cultivars. Furthermore, the degree of structural penetrability of sweetpotatoes, as indexed by penetration resistances, showed very significant correlations with fracturability of fried chips.

No abstract