INIERMEDIARY METABOLISM OF CHOLESTEROL 403 



destroying cholesterol, were Aerobader (Bacterium) aerogenes and the 

 saprophytic flagellate, Pseudomonas jaegeri. 2,4-Dinitrophenol and nico- 

 tinamide significantly stimulated the oxidation of cholesterol by resting 

 cell suspensions of A. aerogenes. 



Stadtman and co-workers^"^ obtained a cholesterol dehydrogenase from 

 the cell-free extracts of a soil Mycobacterium which was able to catalyze 

 the conversion of cholesterol to A'*-cholestene-3-one. It was found that 

 carbon 4 of the steroid ring was oxidized to CO2 about four times as rapidly 

 by the dehydrogenase as was carbon 26 in the side-chain. The aerobic 

 cholesterol-decomposing microorganism used in their studies was probably 

 identical with the M. cholesterolicum isolated by Tak^"* in 1942, which may 

 be related to the Nocardia spp. (trichomycetes) . In preliminary experi- 

 ments, Tak found that Mycobacterium phlei ("timothy bacillus," a lym- 

 phatic pathogen from soil and grass) , M. lacticola (a saprophyte from dairy 

 products), M. berolinense (a saprophyte related to M. lacticola), M. (No- 

 cardia) salmonicolor (soil bacterium), and M. rubrum (from garden soil) all 

 developed well in a mineral cholesterol medium. The fact that the ability 

 to decompose cholesterol is apparently common to all species of Mycobac- 

 terium may be useful in distinguishing between representatives of the 

 general Mycobacterium and Corynebacterium (parasite pathogenic for warm- 

 blooded animals). 



Turfitt^''^'"^^^ suggested that the soil organisms decomposing cholesterol 

 belong to the genus Proactinomyces. These organisms are of especial inter- 

 est in the breakdown of steroids, inasmuch as their oxidizing action, unlike 

 that reported for other organisms, is not completely inhibited by the pres- 

 ence of the intact Cn side-chain. ^'^^ The species represented were Pro- 

 actinomyces asteroides, P. farcinica, and P. paraffinae, all of which belong to 

 the genus Nocardia. Turfitt^°® was unable to obtain evidence of the de- 

 struction of cholesterol by any other bacteria, by molds, or by actinomyces. 

 The organism which destroys cholesterol in vitro was shown to be Pro- 

 actinomyces erythropolis Gray and Thornton. All of the Proactinomyces 

 tested brought about the oxidation of cholesterol to A^-cholestenone. 

 Turfitt^"'' found that a number of the more common hydroxy-steroids 



303 T. C. stadtman, A. Cherkes, and C. B. Anfinsen, J. Biol. Chem., 206, 511-523 

 (1954). 



304 J. D. Tak, Antonie van Leewenhoek J. Microbiol. Serol, 8, 32-40 (1942). 

 306 G. E. Turfitt, Biochem. J., 37, 115-117 (1943); 38, 492-496 (1944). 



306 G. E. Turfitt, Biochem. J., 4O, 79-81 (1946). 



307 G. E. Turfitt, Biochem. J., J^2, 376-383 (1948). 



308 G. E. Turfitt, /. BacterioL, 47, 487-493 (1944). 



309 G. E. Turfitt, /. BacterioL, 54, 557-562 (1947). 



