HiociiKMicAi, Acii\ i'ni;s 



149 



nu'taholizc <i;Iii('(»s(' ;i(M'(»liic;ill\- t luouiili cit licr 

 ()!• both of twi) p;it liw ;i\'s, the "licxosciiioiio- 

 phosphntc"' ;iii(l I he I'lulxlcii-Mcycrhot' 

 sys|(>m. 



According to Douglas aiul San ('Icmciitc, 

 homogenized suspensions of *S. scabies gi'own 

 under sul)nierged aerated conditions arc al)lc 

 to oxidize glucose, succinate, fumaratc, cit- 

 rat(\ and acetate when placed in a Warhuig- 

 type nianometric icspironietcr. The high 

 endogenous respiration is due to oxidation 

 of nitrogenous substances; the cells also 

 oxidize glutamate, aspartate, threonine, 

 phenylalanine, glycin(\ and A'aline and leu- 

 cine to some extent. It was suggested that 

 tyrosine is oxidized tiirough dihydroxyph(Mi- 

 ylalanine with suliseciuent formation of 

 melanin. Addition of dinitrophenol increases 

 the oxygen uptake l)y cells in contact with 

 pyruvate and a-ketoglutarate, and decreases 

 the uptake in cells metabolizing glucose. 



As pointed out previously, anaerobic acti- 

 nomyces cultures are able to fix CO2 . This 

 has been confirmed by Pine, using C'*, as 

 brought out in Table 31. Succinic acid pro- 

 duced by this organism had a high percent- 

 age of its radioactivity in the methylene 

 carbons: "When grown in the presence of 

 oxN^gen, 90 per cent of the total activity of 

 the succinic acid was found in the methylene 

 carbons as compared to G2 per cent when it 

 was grown anaerobically." 



Butterworth et al. (1955) have shown that 

 a C3-C1 condensation coupled with tricarbox- 

 ylic acid cycle activity is a major pathway 

 of carbon dioxide fixation by S. griseus. The 

 intramolecular distribution of C'^ in glutamic 

 acid, produced by the incorporation of la- 

 l)eled carbon dioxide, confirmed the theory 

 that the tricarboxylic acid cycle operates 

 extensively^ in the terminal respiration of 

 S. griseus. 



Gilmour d al. (1955) demonstrated the 

 oxidation of tricarboxylic acid cycle inter- 

 mediates l\v nonproliferating cells of S. 

 griseus. Succinate and a-ketoglutarate were 



o\i(li/.c(| only at sut)sl i-;ilc coMccnt i;i t ions 

 higher lli.iii iliose normally employed. The 

 cells li;i(l to he preinciih.'ited in older to ob- 

 tain oxidation of fum;iiate, nialate, and 

 citrate, (lilmour ct al. ha\-e further shown 

 that the labeling pattern suggests that glu- 

 tamic acid arises from acetate through ex- 

 tensi\-e operation of the conventional tricar- 

 boxylic acid cycle. The role of this acid 

 cycle in amino acid synthesis is establi.shed 

 by the incorj>oration of radioactixity into 

 mo.st of the amino acids of the cellular pro- 

 tein from proliferating cells utilizing acetate- 

 1-C". 



Accoi'ding to Peilman, most of the studies 

 on the metaboli.sm of carbohydrates by S. 

 griseus tended to indicate that carbon di- 

 oxide is the main metabolic product; no 

 accumulation of significant (luantities of 

 intermediates in this oxidation has l)een re- 

 ported. Some doubt was expressed whether 

 the Krebs tricarboxylic acid cycle operates 

 in S. griseus metabolism of glucose (Garner 

 and Kofli(>r). The report of succinic acid 

 production by other species suggested that 

 at least some of the carbohydrate is metab- 

 olized by these organisms by way of ti car- 

 boxylic acid cycle (Cochrane et al.). Lactic 



T.\BLE 31 



.inaerobic fennctilation of glucose plus carbon 

 dioxide-C^^ by Streptomyces sp. (Pine) 



