A spectrophotometric method for the determination of choline dehydrogenase.
نویسنده
چکیده
The increased oxygen uptake of liver suspensions on the addition of acetylcholine, which was reported by Bernheim and Bernheim in 1933 (2), was shown by Mann and Quastel (3) to be due to the oxidation of choline. Betaine aldehyde was identified as the oxidation product (3). The choline oxidase (CO) system was found by Marm, Woodward, and Quastel (4) to consist partly of a typical dehydrogenase. They demonstrated that, in the presence of choline, rat liver extracts reduced sodium ferricyanide anaerobically and cytochrome c aerobically and concluded that the CO system consisted of choline dehydrogenase (CD), cytochrome c, and cytochrome oxidase. During the course of developing the procedure presented in this paper, it was found (1) that the antimycin-sensitive factor of the succinoxidase and diphosphopyridine nucleotide (DPN) cytochrome c reductase systems (5, 6) was involved in the oxidation of choline by rat liver and kidney. This was confirmed by Ebisuzaki and Williams in a subsequent report (7). Evidence was also obtained (1) implicating the Slater factor (8), believed to be a component of the succinoxidase system required for the transmission of electrons between cytochrome b and cytochrome c, in the CO system. Since both BAL and antimycin inhibit CO, and since the inhibition is reversed by artificial carriers such as methylene blue and brilliant cresyl blue,l it is possible that the two compounds are acting on the same substance, although this has yet to be proved. It should be noted, as pointed out by Edelhoch et al. (9), that the lack of effect of antimycin on a soluble DPN cytochrome c reductase (9) may indicate that the arltibiotic acts on some site in particulate preparations which affects reductase activity and not on the reductase protein per se. While no other component of the CO system has been unequivocally identified, riboflavin (10, 11) in the form of flavin-adenine dinucleotide (7), DPN (12-14), folic acid, Leuconostoc citrovorum factor, vitamin B12, and ascorbic acid (15-18) have all been shown t.o enhance the activity of liver CO. A soluble CD
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عنوان ژورنال:
- The Journal of biological chemistry
دوره 207 2 شماره
صفحات -
تاریخ انتشار 1954