Wimalasena K, Dharmasena S
Department of Chemistry, Wichita State University, KS 67260-0051.
Biochem Biophys Res Commun. 1994 Sep 30;203(3):1471-6. doi: 10.1006/bbrc.1994.2350.
A series of ascorbate derivatives has been used to examine the specificity of the reduction site of ascorbate oxidase. Replacement of the 6-OH group of ascorbic acid with either hydrogen or bromine does not alter the substrate activity significantly. 6-Amino-6-deoxy-L-ascorbic acid is a weak substrate for the enzyme, suggesting that positively charged groups at the 6-position are not well tolerated by the enzyme. The modification of the 5-OH reduces the effective interaction with the enzyme and the replacement of 6-OH with 6-S-phenyl- or 6-O-phenyl groups significantly increases the affinity for the enzyme. Both 2-Amino-6-S-phenyl-L-ascorbic acid and imino-D-glucoascorbic acid are not substrates for the enzyme. The stereoelectronic properties and alternate binding modes of these molecules are being considered to explain these observations. The substrate specificity of the enzyme is compared to the specificity of the reduction site of dopamine beta-monooxygenase.
一系列抗坏血酸衍生物已被用于研究抗坏血酸氧化酶还原位点的特异性。用氢或溴取代抗坏血酸的6-OH基团不会显著改变底物活性。6-氨基-6-脱氧-L-抗坏血酸是该酶的弱底物，这表明该酶对6位带正电荷的基团耐受性不佳。5-OH的修饰降低了与酶的有效相互作用，用6-S-苯基或6-O-苯基取代6-OH显著增加了对酶的亲和力。2-氨基-6-S-苯基-L-抗坏血酸和亚氨基-D-葡糖抗坏血酸都不是该酶的底物。正在考虑这些分子的立体电子性质和交替结合模式来解释这些观察结果。将该酶的底物特异性与多巴胺β-单加氧酶还原位点的特异性进行了比较。
