Mori M, Miura S, Tatibana M, Cohen P P
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7044-8. doi: 10.1073/pnas.77.12.7044.
The precursor of rat liver ornithine transcarbamylase (ornithine carbamoyltransferase; carbamoylphosphate:L-ornithine carbamoyltransferase, EC 2.1.3.3) (pre-ornithine transcarbamylase), which was synthesized in a reticulocyte lysate cell-free system, was converted to an apparently mature form of the enzyme by isolated rat liver mitochondria. The proteolytic processing involved two steps: (i) conversion of pre-ornithine transcarbamylase (39,400 daltons) to a product of about 37,000 daltons and (ii) further conversion to the apparently mature form of the enzyme (36,00 daltons). When mitochondria were subfractionated by digitonin treatment followed by sonication of a mitoplast fraction, the proteolytic activity catalyzing the first step was recovered mainly in a matrix fraction. Some activity was found in an intermembrane space fraction. The enzyme activity in the matrix fraction has an optimal pH at about 7.5. The activity was inhibited almost completely by 2 mM leupeptin and partly by 2 mM antipain but not significantly by other microbial protease inhibitors or serine protease inhibitors. It was inhibited strongly by 2 mM EDTA, 2 mM ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate, 2 mM p-chloromercuriphenylsulfonate, and 2 mM Hg(CH3COO)2 but not by N-ethylmaleimide or iodoacetamide. These results suggest that pre-ornithine transcarbamylase is first transported into the mitochondrial matrix and converted there to the mature form of the enzyme by a novel neutral protease(s).
在无细胞的网织红细胞裂解物系统中合成的大鼠肝脏鸟氨酸转氨甲酰酶（鸟氨酸氨甲酰基转移酶；氨甲酰磷酸：L-鸟氨酸氨甲酰基转移酶，EC 2.1.3.3）（前体鸟氨酸转氨甲酰酶），被分离的大鼠肝脏线粒体转化为该酶的一种明显成熟的形式。蛋白水解加工涉及两个步骤：（i）前体鸟氨酸转氨甲酰酶（39,400道尔顿）转化为约37,000道尔顿的产物，以及（ii）进一步转化为该酶的明显成熟形式（36,00道尔顿）。当通过洋地黄皂苷处理对线粒体进行亚分级分离，随后对线粒体膜间腔组分进行超声处理时，催化第一步的蛋白水解活性主要在基质组分中恢复。在膜间腔组分中发现了一些活性。基质组分中的酶活性在约7.5时具有最佳pH。该活性几乎被2 mM亮肽素完全抑制，部分被2 mM抑肽酶抑制，但未被其他微生物蛋白酶抑制剂或丝氨酸蛋白酶抑制剂显著抑制。它被2 mM乙二胺四乙酸、2 mM乙二醇双（β-氨基乙基醚）-N,N,N',N'-四乙酸、2 mM对氯汞基苯磺酸盐和2 mM醋酸汞强烈抑制，但不被N-乙基马来酰亚胺或碘乙酰胺抑制。这些结果表明，前体鸟氨酸转氨甲酰酶首先被转运到线粒体基质中，并在那里通过一种新型中性蛋白酶转化为该酶的成熟形式。
