title: Alternative carboxylation reactions in type II methylotrophs and the localization of carboxylase activities in the intra-cytoplasmic membranes.
abstract: The peripheral arrangements of the intra-cytoplasmic membranes (ICM) as well as the guanine + cytosine (G + C) content of 63% indicate that our obligate methanotrophic strain M 102 would belong to the type II Methylotrophs. There are no active transport mechanisms for some organic additives, some of which are known to stimulate CO2-fixation. The CO2-acceptor molecules, Pyr (pyruvate) and PEP (phospho-enolpyruvate), must be metabolically intracellularly furnished. More than one carboxylating system could be induced in cell fractions. The carboxylating activities were variably registered in cell-free extracts and fragments. Indications that the site of the carboxylating activities are the ICM are discussed. The fact that the CO2-fixation intensities decreased at about the middle of the active growing phase indicates that the formation of the intermediate C4-compound OAA (oxaloacetate) must be furnished through some reactions by-passing the PEP-carboxylation step. The common serine-pathway for C1-assimilation is rearranged so as to fit in the discussed findings.
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000302:isolation & purification*; D002474:Cell-Free System; D007425:Intracellular Membranes / Q000201:enzymology; D008291:Malate Dehydrogenase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D008772:Methylococcaceae / Q000378:metabolism*; D010071:Oxaloacetates / Q000378:metabolism; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D011770:Pyruvate Kinase / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D008293:Malates; D010071:Oxaloacetates; D011773:Pyruvates; D002245:Carbon Dioxide; D010728:Phosphoenolpyruvate; D008291:Malate Dehydrogenase; D011770:Pyruvate Kinase; D002262:Carboxy-Lyases; D010730:Phosphoenolpyruvate Carboxylase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D008697:Methane