4-Hydroxybenzoate (4HBA) is a naturally occurring aromatic compound, and as a key intermediate metabolite not only for natural products but also for artificial products. There are four 4HBA metabolic pathways: protocacechuate cleavage pathway; catechol cleavage pathway; anaerobic degradation pathway in anaerobes; gentisate cleavage pathway. The last pathway including a NIH shift reaction remains to be elucidated. In this review we emphasized in NIH shift reaction involved in the 4HBA degradation. The key enzymes of each 4HBA metabolic pathway also be introduced. Finally, we described thermophilic Bacillus sp. B1 strain which was capable of degradation of various aromatic compounds including 4HBA, and presented a direction for NIH shift reaction research.
