Botha F C, Turpin D H
Department of Botany, University of the Orange Free State, Bloemfontein 9300, South Africa.
Plant Physiol. 1990 Aug;93(4):1460-5. doi: 10.1104/pp.93.4.1460.
Two isoforms of fructose 1,6-bisphosphatase are present in the green alga Selenastrum minutum. The isoenzymes can be separated with ionexchange chromatography or acid precipitation. The stability of the two isoenzymes differ largely. The acid insoluble enzyme exhibits properties similar to that of the enzyme from the chloroplasts of higher plants, i.e. an alkaline pH optima in the absence of reductant, a lower affinity for substrate, strong inhibition by phosphate, and a low sensitivity to fructose-2,6-bisphosphate and AMP. The more abundant form of the enzyme exhibits several properties indicative of heterotrophic fructose 1,6 bisphosphatases, i.e. a high affinity for substrate and sensitivity toward fructose-2,6-bisphosphate and AMP. but is absolutely dependent on a reductant for stability and activity. Evidence is provided indicating that previously reported purification protocols cause inactivation of one of the isoenzymes which could lead to the erroneous conclusion that algae have a single fructose 1,6-bisphosphatase isoenzyme.
绿藻微小色球藻中存在两种果糖1,6 -二磷酸酶同工型。这些同工酶可用离子交换色谱法或酸沉淀法分离。这两种同工酶的稳定性差异很大。酸不溶性酶表现出与高等植物叶绿体中的酶相似的特性，即在没有还原剂的情况下最适pH呈碱性，对底物的亲和力较低，受磷酸盐强烈抑制，对果糖-2,6 -二磷酸和AMP的敏感性较低。含量较多的那种酶表现出几种表明是异养型果糖1,6 -二磷酸酶的特性，即对底物有高亲和力，对果糖-2,6 -二磷酸和AMP敏感，但稳定性和活性绝对依赖于还原剂。有证据表明，先前报道的纯化方案会导致其中一种同工酶失活，这可能会导致错误的结论，即藻类只有一种果糖1,6 -二磷酸酶同工酶。
