Facile Syntheses of C-Glycosides of Aromatic Compounds

Aspartokinase (ATP: l-aspartate 4-phosphotransferase) was extracted and partially purified 11-fold from an extreme thermophile, Thermus flavus AT–62. The enzyme has a temperature optimum near 75°C and a pH optimum of 7 to 8. The enzyme activity was feedback inhibited 80% by l-threonine at the concentration of 0.1 mm at 60°C. No concerted effect of l-threonine with any other aspartate family amino acids was observed. The aspartokinase and homoserine dehydrogenase activities were eluted at different concentrations of KCl from DEAE-cellulose column. The aspartokinase was not inactivated after 30 min at 70°C, but 30% of the original activity was lost after 30 min at 80°C and rapid inactivation occurred above 85°C. The allosteric sensitivity of the enzyirie was maintained even at 60~80°C but was reduced with the increase of temperature, accompanying desensitization above 80°C. The heat stability of the enzyme activity and of the allosteric sensitivity was discussed in comparison with other allosteric enzymes of thermophiles.