FN3K phosphorylates ketosamines

Proteins can undergo chemical modifications such as glycation, which occurs when glucose and other free aldoses spontaneously react with N-terminal and eta-amino groups of proteins to form Schiff bases, which slowly rearrange to ketosamines or, if the sugar is glucose, fructosamines. Fructosamines can further react slowly and become advanced glycation end products, which are thought to play a role in the pathophysiology of several disorders, especially diabetic complications. Ketosamine-3-kinase (FN3K) and ketosamine-3-kinase-related protein (FN3KRP) can phosphorylate protein-bound or free ketosamines on the third carbon of the sugar moiety and the resultant, unstable ketosamine 3-phosphates decompose under physiological conditions (a process called deglycation). Both enzymes can 3-phosphorylate psicosamines (PsiAm) and ribulosamines (RibAm), but only FN3K can 3-phosphorylate fructosamines (FruAm) as well (Delpierre et al. 2000, 2004).

蛋白质可经历如糖基化等化学修饰过程，此过程发生时，葡萄糖及其他游离醛糖自发地与蛋白质的N端和ε-氨基基团反应，形成席夫碱，这些席夫碱随后缓慢地重排为酮胺或，若糖为葡萄糖，则为果糖胺。果糖胺可以进一步缓慢反应，转变为晚期糖基化终产物，后者被认为在多种疾病的病理生理学中发挥重要作用，尤其是糖尿病并发症。酮胺-3-激酶（FN3K）及酮胺-3-激酶相关蛋白（FN3KRP）能够磷酸化糖基团第三碳上的蛋白质结合或游离酮胺，由此产生的、不稳定的酮胺3-磷酸盐在生理条件下分解（该过程称为脱糖基化）。这两种酶均可3-磷酸化吡哆胺（PsiAm）和核糖胺（RibAm），但仅FN3K能够3-磷酸化果糖胺（FruAm）（Delpierre等，2000，2004）。