Lehrstuhl für Pflanzenphysiologie, Universität Osnabrück, Barbarastrasse 11, D-4500 Osnabrück, Federal Republic of Germany.
Plant Physiol. 1991 May;96(1):1-3. doi: 10.1104/pp.96.1.1.
Assimilation of C, N, and S into organic compounds requires effective and flexible cooperation among the energy-converting, tightly coupled, thylakoid-bound processes and stromal metabolism. Fluctuations of light, temperature, and changing concentrations of the various reducible substrates pose unique regulatory problems to photoautotrophic plant cells. Covalent redox modification of enzyme proteins as mediated by the ferredoxin/thiore-doxin-system is suited to provide short-term adaptation of various enzymatic activities in the chloroplast. This mode of regulation is based on the continuous turnover of interconvertible enzyme forms, as in the systems driven by protein phosphorylation/dephosphorylation, but is particularly adapted to the unique conditions of a compartment performing oxygenic photosynthesis by depending on the simultaneous presence of reducing power and of oxygen. Individual fine control of each of the enzymes subjected to redox modification is achieved by specific metabolites acting as additional positive or negative effectors of the reductive (and/or oxidative) modification reaction. The biochemical prerequisite for such a control is the presence of regulatory (extra) sequences carrying cysteine residues which are subjected to reversible redox changes. Although no common amino acid sequence has yet been identified among the known regulatory peptides, in all cases the evolution of autotrophy should be related to the presence of extrasequences in otherwise very conserved enzyme molecules.
将 C、N 和 S 同化到有机化合物中需要能量转换、紧密偶联、类囊体结合过程与基质代谢之间的有效和灵活的合作。光、温度的波动以及各种可还原底物浓度的变化给自养植物细胞带来了独特的调控问题。通过铁氧还蛋白/硫氧还蛋白系统介导的酶蛋白的共价氧化还原修饰适合于为叶绿体中各种酶活性提供短期适应。这种调节模式基于可相互转化的酶形式的连续周转，如由蛋白磷酸化/去磷酸化驱动的系统，但特别适应于通过同时存在还原力和氧气来进行放氧光合作用的隔室的独特条件。通过特定的代谢物作为还原（和/或氧化）修饰反应的附加正或负效应物，对每个受氧化还原修饰的酶进行单独的精细控制。这种控制的生化前提是存在带有半胱氨酸残基的调节（额外）序列，这些残基可发生可逆的氧化还原变化。尽管在已知的调节肽中尚未发现共同的氨基酸序列，但在所有情况下，自养的进化都应与在其他情况下非常保守的酶分子中存在外序列有关。
