It is hypothesized that the pyrrolidine ring of nicotine is oxidized by NicA to form N-methylmyosmine. The spontaneous ring opening of N-methylmyosmine due to the addition of water generates pseudooxynicotine, which is further oxidized to 3-succinoylpyridine (SP) by NicA through two hypothesized unstable compounds and the removal of methylamine. Alkaloid degradation; nicotine degradation. No similarities to sequences of bacterial dehydrogenase or oxidase are found. Moreover, the reverse transcriptase catalytic domain analysis revealed three possible magnesium binding sites in the nicA sequence. In addition, NicA has no significant homology with other genes for degradation of heterocyclic compounds. Therefore, the sequence of NicA seems to be unique among the sequences of bacterial nicotine catabolic genes and more closely related to sequences of higher organisms (PubMed:19060159). In the N-terminal section; belongs to the bacterial reverse transcriptase family.