芒果中褐变相关酶的酶学性质及结构表征

Enzymatic properties and structure characterization of browning-related enzymes in mango skin

以芒果皮中的褐变相关酶为研究对象,研究纯化后的芒果褐变相关酶的酶学性质及结构。试验采用榨汁、离心、抽滤、浓缩等方法,从芒果皮中提取出粗蛋白,经层析柱纯化,得到纯度较高的2种同工酶P1和P2。以邻苯二酚为底物,采用分光光度法在420nm下测定芒果皮中褐变相关酶的活性,其中P1的最适温度为55℃,最适pH值为7.0,最适底物为邻苯二酚,该酶的分子质量约为100ku。P2活性极低。圆二色谱结果表明,2种酶分别含有32.1%和19.2%的α-螺旋以及43.4%和80.8%的β-折叠。荧光光谱结果表明,P1最大发射波长在358.4nm处,相对荧光强度为207.9。P2最大发射波长在356nm处,相对荧光强度为164.2,两者的荧光基团均处于亲水环境中。2种酶的粒径分布均较为集中,粒径分别在11.696nm与8.721nm处,强度最大,分别达到29.686%与25.369%。

The browning related enzymes in mango skin were investigated.Crude proteins were extracted from mango juicing with centrifugation,filtration and concentration methods and purified by column chromatography.Two isoenzymes,P1 and P2,were purified.Using catechol as substrate,the activity of the enzyme was determined by spectrophotometry at 420 nm.The results showed that the optimal temperature,pH value,substrate for mango P1 was 55℃,7.0,and catechol,respectively.The molecular weight of P1 was 100ku.The activity of P2 was very low.Results of circular dichroism showed that the content ofα-helix andβ-fold of the two enzyme was 32.1% and 19.2%,43.4% and 80.8%,respectively.Result of fluorescence excitation spectra showed that the maximum emission wavelength of P1 and P2was at 358.4nm and 356 nm with the fluorescence intensity of 207.9and 164.2.The particle size distribution of the two enzymes was more concentrated at 11.696 nm and 8.721 nm,reaching 29.686% and25.369%.