Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
FEBS Lett. 2012 Jul 30;586(16):2479-82. doi: 10.1016/j.febslet.2012.06.009. Epub 2012 Jun 19.
Barley limit dextrinase (LD) that catalyses hydrolysis of α-1,6 glucosidic linkages in starch-derived dextrins is inhibited by limit dextrinase inhibitor (LDI) found in mature seeds. LDI belongs to the chloroform/methanol soluble protein family (CM-protein family) and has four disulfide bridges and one glutathionylated cysteine. Here, thioredoxin is shown to progressively reduce disulfide bonds in LDI accompanied by loss of activity. A preferential reduction of the glutathionylated cysteine, as indicated by thiol quantification and molecular mass analysis using electrospray ionisation mass spectrometry, was not related to LDI inactivation. LDI reduction is proposed to cause conformational destabilisation leading to loss of function.
大麦极限糊精酶 (LD) 能够催化淀粉衍生糊精中 α-1,6 糖苷键的水解，而成熟种子中存在的极限糊精酶抑制剂 (LDI) 则会抑制 LD 的活性。LDI 属于氯仿/甲醇可溶性蛋白家族（CM 蛋白家族），含有四个二硫键和一个谷胱甘肽化半胱氨酸。本文显示，硫氧还蛋白能够逐步还原 LDI 中的二硫键，同时伴随着活性的丧失。如采用电喷雾离子化质谱法进行巯基定量和分子量分析所示，优先还原谷胱甘肽化半胱氨酸与 LDI 失活无关。LDI 的还原可能导致构象不稳定，从而导致功能丧失。
