It has been shown that the yeast S. cerevisiae has the ability to synthesize nicotinic acid and NAD from 3-methylpyridine. Fractionation of intracellular yeast proteins established that the fraction of molecular weight 65-90 kDa had the highest activity for transformation of pyridine derivatives into nicotinate. HPLC showed that, in addition to nicotinic acid, nicotinamide was also present in the intermediates during transformation of 3-methylpyridine. The results were consistent with the presence in yeast cells of an enzymatic system that transforms 3-methylpyridine into vitamin PP.Nicotinic acid (NA) is known to be produced chemically from the pyridine derivatives β-picoline (3-methylpyridine, 3-MP) or 3-acetylpyridine (3-AP) [1]. The question of NA production in microbiological conversions was first raised in the 1970s by researchers [2-4] who isolated more than 100 cultures of Mycobacterium, Nocardia, Corynebacterium, and Arthrobacter and others that not only decomposed the pyridine ring but also oxidized alkyl substituents on it without destroying it. Also, the ability to oxidize the methyl on 3-MP was first demonstrated at that time. However, the enzymatic aspects of the microbiological transformation of pyridine derivatives have been poorly studied despite the other successes.We observed previously that local strains of the yeast Saccharomyces cerevisiae 913a-1, which were selected as producers of nicotinamideadeninedinucleotide (NAD), accumulate high concentrations of the coenzyme in the presence of 3-MP and 3-AP [5]. This suggests that enzymatic transformation of these compounds into nicotinate and its subsequent participation in NAD biosynthesis is possible. Therefore, our goal was to find intracellular proteins that are involved in the bioconversion of 3-MP into NA by S. cerevisiae 913a-1.Fermentation of S. cerevisiae 913a-1 biomass in the presence of 3-MP is accompanied by more than a doubling of the intracellular NAD concentration (from 35.6 to 68.2 µg/mL) whereas the free NA content did not change (8.6 µg/mL).However, it should be considered that intracellular NA is an intermediate in many exchange transformations of pyridinenucleotides whereas the intracellular content of free NA is low compared with that of nicotinamide or NAD. Thus, the ability of yeast cells to accumulate high concentrations of NAD indicates that biosynthesis can supply the required amount of NA. The increased intracellular pool of NAD observed in yeast in the presence of 3-MP may be due to its preliminary transformation into nicotinate due to its enzymatic transformation in cytoplasm. According to the literature, various microorganism groups can not only completely degrade pyridine bases but also partially transform them. Thus, the ability of the bacteria Nocardia and Arthrobacter to oxidize under co-oxidation conditions alkylpyridines to the corresponding acids, 3-and 2-MP to nicotinic and picolinic acids, has been demonstrated. Transformation of pyridine into nicotinamide also occurs through NA or other intermediates such as ...