Properties of Transaminases in Tissues of the Pear

Abstract

The activity of Aspartate-[alpha]-ketoglutarate (Asp-KG) and Alanine-[alpha]-ketoglutarate (Alan-KG) transaminase has been measured in fresh and lyophilized pear tissue and in tissue protein precipitated with saturated (NH4)2 SO4. Asp-KG and Alan-KG possess distinctly different pH and temperature optima. Pyridoxal-5-phosphate and the appropriate dehydrogenase must be added to the reaction mixture for maximal activity as measured by the coupled oxidation of reduced di-phosphopyridine nucleotide. Both transaminases were present in the particulate and soluble fractions with a generally higher activity in the latter. The specific activity of Asp-KG decreased with increasing enzyme concentration but the reverse trend was shown for Alan-KG transaminase.