Department of Botany, University of Hawaii Honolulu, Hawaii 96822.
Plant Physiol. 1977 Jul;60(1):122-6. doi: 10.1104/pp.60.1.122.
The spatially separated forms of ornithine transcarbamoylase (EC 2.1.3.3) of different molecular weights coexist in sugarcane (Saccharum sp.). The smaller form of the enzyme (mol wt 79,000) appears to be cytoplasmic, while a larger form (mol wt 224,000) sedimented with mitochondria. The Km of the cytoplasmic enzyme for ornithine was 3.11 mm, while the enzyme in the mitochondrial fraction had a Km of 0.50 mm for this substrate; both enzymes had similar affinity for carbamoyl phosphate (0.12 mm). Characteristics of the smaller ornithine transcarbamoylase are in keeping with a predominantly catabolic function, those of the enzyme which sediments with mitochondria, with an anabolic function. Only the mitochondrial enzyme was regulated in vivo by exogenous arginine.
不同分子量的鸟氨酸氨甲酰基转移酶(EC 2.1.3.3)的空间分离形式共存于甘蔗(Saccharum sp.)中。较小的酶形式(分子量 79,000)似乎是细胞质的,而较大的形式(分子量 224,000)则与线粒体一起沉降。细胞质酶的鸟氨酸 Km 为 3.11mm,而线粒体部分的酶对该底物的 Km 为 0.50mm;两种酶对氨基甲酰磷酸的亲和力相似(0.12mm)。较小的鸟氨酸氨甲酰基转移酶的特征与主要的分解代谢功能相符,而与线粒体一起沉降的酶则具有合成代谢功能。只有线粒体酶在体内受到外源性精氨酸的调节。