PMID: 7085661Jul 25, 1982Paper

A calorimetric study of the interaction of pyridoxal 5'-phosphate with aspartate apoaminotransferase and model compounds.

The Journal of Biological Chemistry
A GiartosioC Turano


Schiff base formation between pyridoxal 5'-phosphate and model compounds of increasing complexity (i.e. L-valine and poly-L-lysine) and between pyridoxal 5'-phosphate and the apoenzyme of aspartate aminotransferase has been analyzed by microcalorimetric methods. The apparent pKa values and protonation enthalpy values for the relevant groups ionizing in the pH 4-9 range have been determined for the Schiff bases of L-valine and of poly-L-lysine. Upon Schiff base formation, the only noticeable change is the lowering of the ring nitrogen pK, accompanied by an increase of the relative delta H. In the poly-L-lysine Schiff base, however, the delta H relative to the protonation of the phosphate dianion becomes more negative. This behavior suggests a multiple interaction between the polymer and the ligand. The intrinsic heat of formation is small (congruent to -1 kcal/mol), of the same order of magnitude for both Schiff bases, and appears to be independent of the nature of the aminic reagent. The heat of reaction of pyridoxal 5'-phosphate with aspartate apoaminotransferase has been determined in the pH 6.2-8.8 range at 19 degrees C and at 25 degrees C. Each isotherm is characterized by a lack of proton evolution, a result that is unexpe...Continue Reading

Related Concepts

SGOT - Glutamate oxaloacetate transaminase
Plasma Protein Binding Capacity
Pyridoxal Phosphate
Schiff Bases

Related Feeds

ASBMB Publications

The American Society for Biochemistry and Molecular Biology (ASBMB) includes the Journal of Biological Chemistry, Molecular & Cellular Proteomics, and the Journal of Lipid Research. Discover the latest research from ASBMB here.