葡聚糖水合二激酶的生物学功能及其应用

Biological function and application of glucan-water dikinase:a review.

葡聚糖水合二激酶(glucan-water dikinase,GWD)催化淀粉发生的磷酸化反应是植物临时淀粉降解的必要过程.该文总结了GWD的结构、生物学功能及其与其他淀粉代谢相关酶类的互作,以及GWD基因的研究进展及其在淀粉改性工艺上的应用现状,展望了GWD在淀粉磷酸化改性工艺上的应用前景,旨在为淀粉生物改性提供一种环境友好型、资源集约型的思路和方法.

Summary Starch phosphorylation is a general phenomenon existing naturally in the plant kingdom. The reaction of phosphorylation catalyzed by the glucan-water dikinase （GWD） is a necessary process during the degradation of the transitory starch in plant. In this review, we summarized the progress made on GWD from the view of its structure, biological functions and its interactions with other enzymes involved in starch metabolism. We also discussed its potential application in starch processing industries to provide environment-friendly methods for starch modification through genetic engineering. Potato GWD gene （StGWD） encodes a protein of 1 461 amino acid residues with a calculated molecular mass of about 160 ku for the entire coding sequence. From the N-terminal to C-terminal of the mature StGWD protein, there is a chloroplast transit peptide domain, two carbohydrate- binding modules, a phosphohistidine domain and nucleotide binding domain in turn. GWD marks sections for glucan hydrolysis via C6 phosphorylation to initiate granule surface hydration, while phosphoglucan water dikinase （PWD）, an isoform of GWD then recognizes these partially solubilized sections and catalyzes C3 phosphorylation of nascent glucans to induce steric strain that breaks the helical structure and prevents recrystallization. The starch in leaves will encounter an excess accumulation if the expression of the GWD is inhibited or decreased. And the overexpression of the enzyme may increase the phosphate content of the natural starch. In vivo, many enzymes related to starch metabolism can interact with the GWD, but the mechanisms of their real interaction are not clear yet. The growth will be profoundly inhibited if plants are encountered with environmental stress. We hypothesizethat higher phosphorylated starch may be accumulated if farmers can make good use of the adversary conditions. However, further research and experimental data are needed to support this hypothesis.