Wong J H, Kiss F, Wu M X, Buchanan B B
Department of Plant Biology, Genetics and Plant Biology Building, University of California, Berkeley, California 94720.
Plant Physiol. 1990 Oct;94(2):499-506. doi: 10.1104/pp.94.2.499.
Three forms of pyrophosphate fructose-6-phosphate 1-phosphotransferase (PFP) were purified from both green and red tomato (Lycopersicon esculentum) fruit: (a) a classical form (designated Q(2)) containing alpha- (66 kilodalton) and beta- (60 kilodalton) subunits; (b) a form (Q(1)) containing a beta-doublet subunit; and (c) a form (Q(0)) that appeared to contain a beta-singlet subunit. Several lines of evidence suggested that the different forms occur under physiological conditions. Q(2) was purified to apparent electrophoretic homogeneity; Q(1) and Q(0) were highly purified, but not to homogeneity. The distribution of the PFP forms from red (versus green) tomato was: Q(2), 29% (90%); Q(1), 47% (6%); and Q(0), 24% (4%). The major difference distinguishing the red from the green tomato enzymes was the fructose-2,6-bisphosphate (Fru-2,6-P(2))-induced change in K(m) for fructose-6-phosphate (Fru-6-P), the ;green forms' showing markedly enhanced affinity on activation (K(m) decrease of 7-9-fold) and the ;red forms' showing either little change (Q(0), Q(1)) or a relatively small (2.5-fold) affinity increase (Q(2)). The results extend our earlier findings with carrot root to another tissue and indicate that forms of PFP showing low or no affinity increase for Fru 6-P on activation by Fru-2,6-P(2) (here Q(1) and Q(0)) are associated with sugar storage, whereas the classical form (Q(2)), which shows a pronounced affinity increase, is more important for starch storage.
从绿色和红色番茄（番茄）果实中纯化出了三种形式的焦磷酸果糖-6-磷酸1-磷酸转移酶（PFP）：（a）一种经典形式（命名为Q(2)），含有α-（66千道尔顿）和β-（60千道尔顿）亚基；（b）一种形式（Q(1)），含有β-双重亚基；（c）一种形式（Q(0)），似乎含有β-单一亚基。几条证据表明，不同形式在生理条件下出现。Q(2)被纯化至表观电泳纯；Q(1)和Q(0)被高度纯化，但未达到纯一。红色（相对于绿色）番茄中PFP形式的分布为：Q(2)，29%（90%）；Q(1)，47%（6%）；Q(0)，24%（4%）。区分红色和绿色番茄酶的主要差异是果糖-2,6-二磷酸（Fru-2,6-P(2)）诱导的对果糖-6-磷酸（Fru-6-P）的K(m)变化，“绿色形式”在激活时显示出明显增强的亲和力（K(m)降低7至9倍），而“红色形式”显示出几乎没有变化（Q(0)、Q(1)）或相对较小（2.5倍）的亲和力增加（Q(2)）。这些结果将我们早期对胡萝卜根的研究结果扩展到了另一种组织，并表明在Fru-2,6-P(2)激活时对Fru 6-P亲和力增加较低或没有增加的PFP形式（这里是Q(1)和Q(0)）与糖储存相关，而显示出明显亲和力增加的经典形式（Q(2)）对淀粉储存更重要。
