Isolation of a delta7-cholesterol desaturase from Tetrahymena thermophila.
Cell-free preparations of Tetrahymena thermophila catalyze the direct desaturation of cholesterol to delta7-dehydrocholesterol (provitamin D3). The activity was isolated in the microsomal fraction from Tetrahymena homogenates. Delta7-desaturase activity was stimulated fivefold by the addition of 6 mM ATP. Other cofactors assayed, including NAD, NADP, NADH or NADPH, had no significant effect. The activity was found in microsomes prepared from stationary-phase cultures of the ciliate, grown either with or without added cholesterol, thus indicating that it is constitutively expressed in T. thermophila cells.
Valcarce
G
G
Department of Industrial Microbiology and Biotechnology, School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina.
Florin-Christensen
J
J
Nudel
C
C
D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D003470:Culture Media; D008861:Microsomes / Q000201:enzymology; D010088:Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D016808:Tetrahymena thermophila / Q000201:enzymology* / Q000254:growth & development
D003470:Culture Media; C033144:lathosterol delta-5-dehydrogenase; D002784:Cholesterol; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors