ENZYME VARIATION IN MICRO‐ORGANISMS

作者：John S Yudkin · 发表于：Biological reviews/Biological reviews of the Cambridge Philosophical Society · 年份：1938 · DOI：10.1111/j.1469-185x.1938.tb00508.x · 被引用次数：92 · 研究领域：Microbial Metabolic Engineering and Bioproduction、Photosynthetic Processes and Mechanisms、Origins and Evolution of Life

Summary The increase in enzyme content in micro‐organisms may be classified according to the type of substance responsible for the increase. First, as has been suggested by Jacoby, the substance may be necessary to the cell as a “brick” for the building up of the enzyme molecule. Secondly, the substance may be the substrate of the enzyme or some closely related compound. A substance in this class may act either directly on the individual cell or as a selecting agent during growth of cells in which the enzyme has appeared as a mutation. Examples of direct chemical interaction between cell and substrate (adaptation) are the hydrogenlyase of Bact. coli and the galactozymase of yeast; examples of mutation and selection occur amongst organisms of the Bact. coli mutabile type. As would be expected, when organisms possessing a newly acquired enzyme are grown in the absence of the substrate, enzymes arising by adaptation are readily lost whilst enzymes arising by mutation and selection tend to be permanent. It would also be expected that the former type of enzyme production would occur in the absence of cell division; for natural selection to operate, however, cell division is essential. Many unsatisfactory attempts have been made to show the dependence or otherwise of certain examples of enzyme production on cell division, such as the study of enzyme production in the presence or absence of suitable growth substances or of poisons. By counting experiments, however, it has been clear...