2-(guanylformylmethoxy)-3-(triphospho)propanal and sodium-cyanoborohydride

Ca2+ and GTP are the main modulators of type-2 transglutaminases. To study the interaction of the enzyme with GTP, we have employed periodate-oxidized GTP as an affinity-label probe. Dialdehyde GTP bound irreversibly to type-2 transglutaminase in a time-dependent way with 1:1 stoichiometry at complete modification. The reaction took place in the absence, but was more rapid in the presence, of cyanoborohydride. Native GTP prevented incorporation of dialdehyde GTP, and Ca2+ significantly slowed down the reaction rate. The modified enzyme displayed decreased sensitivity to Ca2+, with a sigmoid saturation curve. We conclude that type-2 transglutaminase has a single GTP-binding site, the modification of which by dialdehyde GTP mimics nucleotide binding to the enzyme.

Topics: Affinity Labels; Binding Sites; Borohydrides; Calcium; Erythrocytes; Guanosine Triphosphate; Humans; Oxidation-Reduction; Periodic Acid; Transglutaminases