Lunn John Edward
Commonwealth Scientific and Industrial Research Organization, Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia.
Plant Physiol. 2002 Apr;128(4):1490-500. doi: 10.1104/pp.010898.
Cyanobacteria and proteobacteria (purple bacteria) are the only prokaryotes known to synthesize sucrose (Suc). Suc-P synthase, Suc-phosphatase (SPP), and Suc synthase activities have previously been detected in several cyanobacteria, and genes coding for Suc-P synthase (sps) and Suc synthase (sus) have been cloned from Synechocystis sp. PCC 6803 and Anabaena (Nostoc) spp., respectively. An open reading frame in the Synechocystis genome encodes a predicted 27-kD polypeptide that shows homology to the maize (Zea mays) SPP. Heterologous expression of this putative spp gene in Escherichia coli, reported here, confirmed that this open reading frame encodes a functional SPP enzyme. The Synechocystis SPP is highly specific for Suc-6(F)-P (K(m) = 7.5 microM) and is Mg(2+) dependent (K(a) = 70 microM), with a specific activity of 46 micromol min(-1) mg(-1) protein. Like the maize SPP, the Synechocystis SPP belongs to the haloacid dehalogenase superfamily of phosphatases/hydrolases. Searches of sequenced microbial genomes revealed homologs of the Synechocystis sps gene in several other cyanobacteria (Nostoc punctiforme, Prochlorococcus marinus strains MED4 and MIT9313, and Synechococcus sp. WH8012), and in three proteobacteria (Acidithiobacillus ferrooxidans, Magnetococcus sp. MC1, and Nitrosomonas europaea). Homologs of the Synechocystis spp gene were found in Magnetococcus sp. MC1 and N. punctiforme, and of the Anabaena sus gene in N. punctiforme and N. europaea. From analysis of these sequences, it is suggested that Suc synthesis originated in the proteobacteria or a common ancestor of the proteobacteria and cyanobacteria.
蓝细菌和变形菌（紫色细菌）是已知能合成蔗糖（Suc）的仅有的原核生物。蔗糖磷酸合酶、蔗糖磷酸酶（SPP）和蔗糖合酶活性先前已在几种蓝细菌中检测到，并且分别从聚球藻属PCC 6803和鱼腥藻属（念珠藻属）中克隆出了编码蔗糖磷酸合酶（sps）和蔗糖合酶（sus）的基因。聚球藻基因组中的一个开放阅读框编码一种预测的27-kD多肽，该多肽与玉米（玉米）的SPP具有同源性。本文报道了该假定的spp基因在大肠杆菌中的异源表达，证实了这个开放阅读框编码一种功能性的SPP酶。聚球藻SPP对蔗糖-6（F）-P具有高度特异性（K(m) = 7.5 microM），并且依赖Mg(2+)（K(a) = 70 microM），比活性为46微摩尔·分钟(-1)·毫克(-1)蛋白质。与玉米SPP一样，聚球藻SPP属于磷酸酶/水解酶的卤代酸脱卤酶超家族。对已测序的微生物基因组的搜索揭示了在其他几种蓝细菌（点状念珠藻、海洋原绿球藻菌株MED4和MIT9313以及聚球藻属WH8012）以及三种变形菌（嗜酸氧化亚铁硫杆菌、磁球菌属MC1和欧洲亚硝化单胞菌）中存在聚球藻sps基因的同源物。在磁球菌属MC1和点状念珠藻中发现了聚球藻spp基因的同源物，在点状念珠藻和欧洲亚硝化单胞菌中发现了鱼腥藻sus基因的同源物。通过对这些序列的分析，表明蔗糖合成起源于变形菌或变形菌和蓝细菌的共同祖先。
