【摘要】 分离和纯化了的水稻和小麦黄化苗中的PAL,经聚丙烯酰胺凝胶电泳及SDS-聚丙烯酰胺凝胶电泳检验均为单一的蛋白带。水稻、小麦的PAL都具有一定的耐热性,但前者略高于后者;两者的最适pH都在碱侧,前者为9.2,后者为8.8;并均能被巯基试剂NEM所抑制。此外,水稻的PAL比活远较小麦的高;水稻只有一个K_m值,为5.94×10¹⁴M,而小麦则有二个,即K_m^L=0.625×10^-4和K_m^H=3.1×10^-4M。分析不同来源PAL的氨基酸百分组成,发现水稻的酸性氨基酸成分少于小麦;而中性及碱性氨基酸成分则高于小麦。用SDS电泳测得小麦亚基分子量为70,000而水稻则为57,500,推测小麦、水稻PAL全酶分子量分别为280,000与230,000道尔顿。更多还原

【Abstract】 Rice and wheat PAL have been isolated and purified to homogeneity by ammonium sulphate fractionation, DEAE-cellulose chromatography and affinity chromatography on L-Phe-Sepharose column. The purity was identifited by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulphate （SDS）.Many properties of the two PALs are roughly similar, but there are some differences.Both PALs possess certain thermostability and rice PAL is more thermostable than wheat PAL. The optimum pH of the two PALs are both in the alkaline side, but the optimum pH of the PAL of rice is slightly higher than that of wheat, being 9.2 and 8.8, respectively. Both PALs were inhibited by sulfhydryl reagent, NEM. The final specific activities of rice and wheat PAL were 1350 and 454u （mg protien）^-1 respectively.The K_m values for rice PAL has been shown to be 5.94×10^-4M, whereas the wheat PAL possess two K_m values — 3.1×10^-4M and 0.625×10^-4M.The results of amino acid analysis of PAL show that rice PAL contains less dicarboxylic amino acids and more neutral and basic amino acids than wheat PAL.The molecular weight of rice PAL subunit is 57,500 and that of wheat is 70,000 as assayed by SDS polyacrylamide gel electrophoresis. The subunit of either PAL migrated as a single band. Since the PALs consist of four similar subunits, the total enzyne molecular weights of rice and wheat PALs should be about 230,000 and 280,000 Dal., respectively.更多还原