Pardo A D, Chereskin B M, Castelfranco P A, Franceschi V R, Wezelman B E
Department of Botany, University of California, Davis, California 95616.
Plant Physiol. 1980 May;65(5):956-60. doi: 10.1104/pp.65.5.956.
The synthesis of Mg-protoporphyrin-IX from exogenous protoporphyrin-IX, in a crude plastid pellet extracted from greening cucumber cotyledons was found to require l-glutamate as a cofactor. It has now been shown that glutamate acts in the presence of contaminating mitochondria to provide an ATP regenerating system. With purified plastids, Mg chelatase is not stimulated by glutamate; instead, it requires a high concentration of ATP and is greatly stimulated by added phosphoenolpyruvate and pyruvate kinase. GTP, UTP, CTP, and ITP will not substitute for ATP. ADP in the absence of an ATP generating system is completely ineffective, whereas it is slightly inhibitory in the presence of 10 mm ATP. AMP is strongly inhibitory in the reaction; 50% inhibition is obtained at approximately 3.5 mm AMP in the presence of 10 mm ATP.
在从绿化黄瓜子叶中提取的粗质体沉淀中，由外源原卟啉-IX合成镁原卟啉-IX被发现需要L-谷氨酸作为辅因子。现已表明，谷氨酸在存在污染线粒体的情况下发挥作用，以提供一个ATP再生系统。对于纯化的质体，镁螯合酶不受谷氨酸刺激；相反，它需要高浓度的ATP，并且添加磷酸烯醇丙酮酸和丙酮酸激酶会对其有极大的刺激作用。GTP、UTP、CTP和ITP不能替代ATP。在没有ATP生成系统的情况下，ADP完全无效，而在存在10 mM ATP时它有轻微抑制作用。AMP在该反应中有强烈抑制作用；在存在10 mM ATP时，约3.5 mM AMP可产生50%的抑制作用。
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