Plants, green algae, and cyanobacteria synthesize storage polysaccharides by a similar ADPglucose-based pathway. Plant starch metabolism can be distinguished from that of bacterial glycogen by the presence of multiple forms of enzyme activities for each step of the pathway. This multiplicity does not coincide with any functional redundancy, as each form has seemingly acquired a distinctive and conserved role in starch metabolism. Comparisons of phenotypes generated by debranching enzyme-defective mutants in Escherichia coli and plants suggest that enzymes previously thought to be involved in polysaccharide degradation have been recruited during evolution to serve a particular purpose in starch biosynthesis. Speculations have been made that link this recruitment to the appearance of semicrystalline starch in photosynthetic eukaryotes. Besides the common core pathway, other enzymes of malto-oligosaccharide metabolism are required for normal starch metabolism. However, according to the genetic and physiological system under study, these enzymes may have acquired distinctive roles.

中文翻译：

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从细菌糖原到淀粉：了解植物淀粉颗粒的生物起源

植物、绿藻和蓝藻通过类似的基于 ADP 葡萄糖的途径合成储存多糖。植物淀粉代谢与细菌糖原代谢的区别在于，该途径的每个步骤都存在多种形式的酶活性。这种多样性与任何功能冗余并不相符，因为每种形式似乎都在淀粉代谢中获得了独特而保守的作用。对大肠杆菌和植物中酶缺陷突变体脱支产生的表型的比较表明，先前被认为参与多糖降解的酶已在进化过程中被招募，以在淀粉生物合成中发挥特殊作用。已经做出推测，将这种招募与光合真核生物中半结晶淀粉的出现联系起来。除了共同的核心途径，正常的淀粉代谢还需要麦芽寡糖代谢的其他酶。然而，根据所研究的遗传和生理系统，这些酶可能具有独特的作用。