Pajula R L, Raina A, Eloranta T
Eur J Biochem. 1979 Nov;101(2):619-26. doi: 10.1111/j.1432-1033.1979.tb19756.x.
Spermine synthase, a propylamine transferase, which catalyses the biosynthesis of spermine from S-methyladenosylhomocystemine and spermidine has been purified to an apparent homogeneity (about 6000-fold) from bovine brain using spermine-Sepharose affinity chromatography. The enzyme preparation was free from S-adenosylmethionine decarboxylase and spermidine synthase activities. The molecular Stokes radius of the enzyme was calculated to be 4.16 nm. The enzyme has an apparent molecular weight of approximately 88 000, composing of two subunits of equal size. The enzyme showed a broad pH optimum between 7.0 and 8.0 and an acidic isoelectric point at pH 5.10. The apparent Km values for S-methyladenosylhomocysteamine was 0.6 microM and about 60 microM for spermidine. The enzyme showed strict specificity to spermidine as the propylamine acceptor. Both the reaction products, spermine and 5'-methylthioadenosine inhibited the enzyme activity, methylthioadenosine being a powerful competitive inhibitor with respect to S-methyladenosylhomocysteamine (Ki value of about 0.3 microM). Putrescine also inhibited competitively with respect to spermidine (Ki value of about 1.7 mM). Spermine synthase had no requirements for metal or other cofactors.
精胺合酶是一种丙胺转移酶，它催化由S - 甲基腺苷高半胱氨酸和亚精胺生物合成精胺。利用精胺 - 琼脂糖亲和色谱法，已从牛脑中纯化出该酶，其纯度达到表观均一性（约6000倍）。该酶制剂不含S - 腺苷甲硫氨酸脱羧酶和亚精胺合酶活性。计算得出该酶的分子斯托克斯半径为4.16纳米。该酶的表观分子量约为88000，由两个大小相等的亚基组成。该酶在pH 7.0至8.0之间表现出较宽的最适pH值，其酸性等电点为pH 5.10。S - 甲基腺苷高半胱氨酸的表观Km值为0.6微摩尔，亚精胺的表观Km值约为60微摩尔。该酶对作为丙胺受体的亚精胺表现出严格的特异性。两种反应产物，精胺和5'-甲硫基腺苷均抑制该酶活性，甲硫基腺苷是相对于S - 甲基腺苷高半胱氨酸的强效竞争性抑制剂（Ki值约为0.3微摩尔）。腐胺也相对于亚精胺竞争性抑制（Ki值约为1.7毫摩尔）。精胺合酶对金属或其他辅因子没有需求。
