The versatility of reactions catalyzed by pyridoxal 5′-phosphate (PLP) enzymes is largely due to the chemistry of their extraordinary catalyst. PLP is necessary for many reactions involving amino acids. Reaction specificity is controlled by the orientation of the external aldimine intermediate that is formed upon addition of the amino acidic substrate to the coenzyme. The breakage of a specific bond of the external aldimine gives rise to a carbanionic intermediate. From this point, the different reaction pathways diverge leading to multiple activities: transamination, decarboxylation, racemization, elimination, and synthesis. A significant novelty appeared approximately 30 years ago when it was reported that some PLP-dependent decarboxylases are able to consume molecular oxygen transforming an amino acid into a carbonyl compound. These side paracatalytic reactions could be particularly relevant for human health, also considering that some of these enzymes are responsible for the synthesis of important neurotransmitters such as γ-aminobutyric acid, dopamine, and serotonin, whose dysregulation under oxidative conditions could have important implications in neurodegenerative states. However, the reactivity of PLP enzymes with dioxygen is not confined to mammals/animals. In fact, some plant PLP decarboxylases have been reported to catalyze oxidative reactions producing carbonyl compounds. Moreover, other recent reports revealed the existence of new oxidase activities catalyzed by new PLP enzymes, MppP, RohP, Ind4, CcbF, PvdN, Cap15, and CuaB. These PLP enzymes belong to the bacterial and fungal kingdoms and are present in organisms synthesizing bioactive compounds. These new PLP activities are not paracatalytic and could only scratch the surface on a wider and unexpected catalytic capability of PLP enzymes.

吡ido醛5'-磷酸（PLP）酶催化反应的多功能性在很大程度上是由于其非常规催化剂的化学性质。对于许多涉及氨基酸的反应，PLP是必需的。反应特异性由外部醛亚胺中间体的取向控制，该中间体是在将氨基酸底物添加到辅酶后形成的。外部醛亚胺的特定键的断裂产生碳负离子中间体。从这一点出发，不同的反应途径有所不同，从而导致多种活性：氨基转移，脱羧，外消旋，消除和合成。大约30年前出现了一个重大的新颖性，当时有报道称某些PLP依赖性脱羧酶能够消耗分子氧，从而将氨基酸转化为羰基化合物。这些副催化副反应可能与人类健康特别相关，还考虑到其中某些酶负责重要神经递质的合成，例如γ-氨基丁酸，多巴胺和5-羟色胺，它们在氧化条件下的失调可能对神经变性产生重要影响。状态。然而，PLP酶与双氧的反应性并不局限于哺乳动物/动物。实际上，已经报道了一些植物PLP脱羧酶催化产生羰基化合物的氧化反应。此外，最近的其他报道揭示了由新的PLP酶MppP，RohP，Ind4，CcbF，PvdN，Cap15和CuaB催化的新氧化酶活性的存在。这些PLP酶属于细菌和真菌界，存在于合成生物活性化合物的生物中。