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Nutritional requirement of complete coenzymes in place of, or in preference to, the vitamin moieties (e.g., nicotinamide, thiamine) of their respective molecules is apparently not common even among parasitic organisms. Lwoff and Lwoff (1936a, b. 1937a, b) demonstrated that preparations of codehydrogenases I and II satisfy the V-factor requirement of Hemophilus parainfluenzae whereas nicotinamide does not. Their results were confirmed by a number of investigators, chiefly in the course of developing and using assay methods for experimental and clinical studies, using both Hemophilus parainfluenzae (Kohn et al.. 1938-1940, Pittman and Fraser 1940, Dann, Handler et al. 1941, 1942, and others) and Hemophilus influenzae (Vilter et al. 1939, 1940, Hoagland et al. 1942, 1943, and others). It was further shown that these organisms are able to utilize nicotinamide riboside in place of V-factor although rather poorly as compared with codehydrogenase I (Schlenk and Gingrich, 1942). In this connection it is interesting to mention the fact that the growth response of Streptococcus saliarius is better in the presence of cocarboxylase than with thiamine (Niven and Smiley, 1943). The fact that the codehydrogenases can be substituted for V-factor has led to the use of hemophilic bacteria for attempts to develop assay methods for the coenzymes in tissue fluids, extracts and excretions. Although the results are somewhat divergent the findings indicate generally that the V-factor content of blood is not related to the intake of nicotinamide nor to deficiency thereof, but that it is reduced in liver and muscle of dogs suffering from blacktongue. This agrees with the results of Axelrod et al. (1939, 1941) for the codehydrogenase I content of tissues as determined by the fermentation test. That the microbiological assay methods have not come into general use is to be explained partly by the fact that blood determinations fail to yield a ready means of diagnosing nicotinamide deficiency and also to the variability of the growth response of the organisms and the difficulty of interpreting results in absolute terms unless relatively pure preparations of codehydrogenase are used for reference. Our attention has been directed particularly to the questions as to (1) which compounds satisfy the V-factor requirement and (2) how they may be utilized in comparison to codehydrogenase I. In attempting to reach reasonably tenable conclusions we have considered the use of pure compounds of primary importance and are confident of having satisfied the requirements in this respect (Schlenk, 1942a). The indications of the results relative to the function of V-factor and

Codehydrogenase I and Other Pyridinium Compounds as V-Factor for Hemophilus influenzae and H. parainfluenzae