Bergamini C M, Signorini M
Instituto di Chimica Biologica, Università di Ferrara, Italy.
Biochem J. 1993 Apr 1;291 ( Pt 1)(Pt 1):37-9. doi: 10.1042/bj2910037.
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.
钙离子（Ca²⁺）和鸟苷三磷酸（GTP）是2型转谷氨酰胺酶的主要调节剂。为了研究该酶与GTP的相互作用，我们使用了高碘酸盐氧化的GTP作为亲和标记探针。二醛GTP以1:1的化学计量比与2型转谷氨酰胺酶发生不可逆的结合，且在完全修饰时呈时间依赖性。该反应在没有氰基硼氢化钠的情况下也能发生，但在有氰基硼氢化钠存在时反应更快。天然GTP可阻止二醛GTP的掺入，而Ca²⁺可显著减慢反应速率。修饰后的酶对Ca²⁺的敏感性降低，呈现出S形饱和曲线。我们得出结论，2型转谷氨酰胺酶有一个单一的GTP结合位点，二醛GTP对其的修饰模拟了核苷酸与该酶的结合。
