CHAPTER 9 



Biochemical Activities 



The manifold aspects of the biochemistry 

 of actinomycetes are still far from elucidated. 

 Nevertheless, considerable progress has been 

 made in recent years in our understanding of 

 some of the chemical mechanisms involved 

 in the growth and activities of these organ- 

 isms. By far the greatest number of investi- 

 gations on the activities of actinomycetes 

 have been concerned largely with antibiotic 

 production and the mode of action of anti- 

 biotics. Limited consideration has also been 

 given to certain other fundamental princi- 

 ples of actinomycete biochemistry. 



Respiration 



Hockenhull et al. reported that, under 

 highly aerobic conditions, glucose was con- 

 verted by S. griseus mainly to cell material 

 and CO2 . Under restricted aeration, lactic 

 acid was also formed. Pyruvic acid was pro- 

 duced during the stages of most rapid 

 growth. The metabolism of glucose by acti- 

 nomycetes was dependent upon the presence 

 of phosphate, the optimal hydrogen-ion con- 

 centration for both glucose oxidation and 

 the rate of disappearance of inorganic phos- 

 phate being about pH 7. At pH 7.3, there 

 was a gradual increase in glucose utilization 

 from 0.62 mg/ml, in the absence of phos- 

 phate, to 1.64 mg/ml, in presence of 0.01 M 

 potassium phosphate. Further increases in 

 phosphate concentration did not affect the 

 utilization of the sugar. 



Phosphate esters, tentati\'ely identified as 

 glucose 1 -phosphate and glucose 6-phos- 



phate, were obtained by Hockenhull in fluo- 

 ride-inhibited systems. Glucose oxidation 

 was depressed by 10~^ M sodium iodoacetate 

 and by 10~^ M sodium arsenite, but was 

 stimulated by 10~- M sodium arsenate; 

 10-=^ M 2,4-dinitrophenol and 10-« M so- 

 dium azide had no effect. Streptomycin pro- 

 duction was decreased by 3 X 10~^ M so- 

 dium arsenate but not by 10~- M sodium 

 fluoride or 10~^ M sodium iodoacetate. *S. 

 griseus metabolized members of the tricar- 

 boxylic acid cycle, although citrate and a- 

 ketoglutarate gave much lower values of 

 CO2 at pH 7.3 than did pyruvate, acetate, 

 succinate, fumarate, or malate. Keto acids 

 were produced, in presence of arsenite, from 

 fumarate, malate, glucose, lactate, acetate, 

 succinate, glutamate, and citrate in descend- 

 ing order of yield. Except from fumarate, 

 which yielded some material behaving like 

 a-ketoglutarate, the product was chiefly 

 pyruvate. 



According to Cochrane and Hawley, ri- 

 bose 5-phosphate is oxidized by extracts of 

 S. codicolor almost to completion, in a series 

 of reactions dependent on triphosphopyri- 

 dine nucleotide, stimulated l:)y thiamine 

 pj^rophosphate, and insensitiA'e to iodoace- 

 tate. Fructose 1 ,6-diphosphate is dephos- 

 phorylated by one or more enzymes, with 

 optimal activity at pH 4.5 to 5.0; it also can 

 be oxidized by triphosphopyridine nucleo- 

 tide-dependent reactions, involving glucose 

 6-phosphate as an intermediate. The con- 

 clusion was reached that S. coelicolor can 



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