Measurement of Activation Energy of γ-Glutamyltransferase as a Marker for Enzyme Heterogeneity

Abstract

Summary:In order to detect differences between various multiple forms of γ-glutamyltransferase, the activation energy was measured. In the serum of patients with liver diseases, activation energy was measured. In the serum of patients with liver diseases, activation engergy of the serum enzyme is higher than in normal individuals (41.9 ±1.2 vs. 38.9 + 1.5 kJ/mol, p < 0.05). Neuraminidase treatment resulted in a reduction of activation energy. Various multiple forms of serum γ-glutamyltransferase, as prepared by lectin affinity chromatography (concanavalin A, Ricinus communis I and II, wheat germ agglutinin) showed activation energy differences between binding and nonbinding fractions. Similar results were observed in seminal plasma γ-glutamyltransferase, when patients with accessory gland infection were compared with a reference population. Our results suggest that the activation energy depends upon differences in the carbohydrate part of the enzyme. The low γ-glutamyltransferase activation energy of tissue extracts increased significantly after butanol extraction and was then comparable with serum activation energy values, which suggests that lipid-binding is a factor in activation energy variation. In most cases, γ-glutamyltransferase activities measured at a certain temperature can be easily converted to a corresponding activity at another temperature, but in severe liver disease significant errors may be introduced when simple temperature conversion factors are used.

Short Communication

“…The lowering of the activation energy obtained after neuraminidase treatment suggests that the presence of sialic acid can be regarded äs a steric hindrance for the active site of the -glutamyltransferase (11). Removal of terminal fucose residues (12), galactose or N-acetyl-Z)-glucosamine (11) induces minor effects on the activation energy.…”

“…Delanghe et al have shown that both affmity chromatography behaviour (12) and activation energy (11,12) are independent of total serum -glutamyltransferase activity. Similarly, we have not found a significant correlation between the total serum S'-nucleotidase activity and activation energy.…”