Genetic Diversity of Bangladeshi Jackfruit (Artocarpus heterophyllus) over Time and Across Seedling Sources

Economic Botany - Crop genetic diversity is important, but may be lost due to intentional or non-intentional selection processes. Jackfruit (Artocarpus heterophyllus) is the national fruit of...     

Selectivity in vitamin B-6 model reactions: Selective α or β deuteration of amino acids under transamination or racemization conditions

Al(III)-catalyzed reactions of vitamin B-6 (pyridoxal)-amino acid schiff bases have been studied in ²H₂O. By using excess of the amino acid and varying conditions, amino acids selectively deuterated in the α-position, the β-position, or in both α- and β-positions are isolated. Reaction conditions are those of model systems in which amino acids are known to be reversibly transaminated and racemized by pyridoxal and Al(III). The racemization reaction leads to α-deuteration of the amino acid while transamination followed by its reverse leads to both α- and β-deuteration. The two reactions are viewed as passing through a common dihydropyridine intermediate. The Al(III) serves as an interesting model for the enzyme in that it not only catalyzes transamination and racemization but also can be made to select which of these reactions predominates. This selective catalysis of these reactions is attributed to strong and different pH dependence of the reactivity of various sites of the dihydropyridine intermediate for vitamin B-6 catalysis when incorporated in an Al(III) complex. The biochemical importance of this selectivity and the practical extension of the method of deuteration to other amino acids is discussed.