title: Factors affecting the level of alanine racemase in Escherichia coli.
abstract: Alanine racemase occupies a key position in the alanine branch of peptidoglycan biosynthesis. The level of this enzyme in Escherichia coli W is a function of the carbon source. For example, growth on l-alanine causes a 25-fold higher level of alanine racemase when compared with growth on glucose. When potential inducers of this enzyme are added to either a glucose or succinate medium, a low specificity is observed with those compounds that cause higher levels of enzyme. Growth of E. coli W on either pyruvate, d-alanine, or l-alanine resulted in lower levels of l- and d-alanine in the internal pool. With each of these carbon sources, the level of alanine racemase was markedly elevated when compared to glucose-grown cells; thus, with single carbon sources, the concentration of alanine in the pool is inversely related to the specific activity of alanine racemase. These observations support derepression as a possible mechanism that gives rise to higher levels of alanine racemase. Since multiple forms of the alanine racemase were not detected in extracts from E. coli W grown on various carbon sources, it would appear that this type of heterogeneity is not a consideration in interpreting the above results.
mesh_terms: D000409:Alanine / Q000378:metabolism; D002247:Carbon Isotopes; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D002852:Chromatography, Ion Exchange; D003470:Culture Media; D003956:Dialysis; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006358:Hot Temperature; D007535:Isomerases / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D013237:Stereoisomerism; D013386:Succinates / Q000378:metabolism; D013395:Sucrose
chemical_list: D002247:Carbon Isotopes; D003470:Culture Media; D011773:Pyruvates; D013386:Succinates; D013395:Sucrose; D007535:Isomerases; D005947:Glucose; D000409:Alanine; D005990:Glycerol