| First Author | Bunker RD | Year | 2013 |
| Journal | J Biol Chem | Volume | 288 |
| Issue | 3 | Pages | 1643-52 |
| PubMed ID | 23179721 | Mgi Jnum | J:323239 |
| Mgi Id | MGI:7262841 | Doi | 10.1074/jbc.M112.427997 |
| Citation | Bunker RD, et al. (2013) Structure and function of human xylulokinase, an enzyme with important roles in carbohydrate metabolism. J Biol Chem 288(3):1643-52 |
| abstractText | D-Xylulokinase (XK; EC 2.7.1.17) catalyzes the ATP-dependent phosphorylation of d-xylulose (Xu) to produce xylulose 5-phosphate (Xu5P). In mammals, XK is the last enzyme in the glucuronate-xylulose pathway, active in the liver and kidneys, and is linked through its product Xu5P to the pentose-phosphate pathway. XK may play an important role in metabolic disease, given that Xu5P is a key regulator of glucose metabolism and lipogenesis. We have expressed the product of a putative human XK gene and identified it as the authentic human d-xylulokinase (hXK). NMR studies with a variety of sugars showed that hXK acts only on d-xylulose, and a coupled photometric assay established its key kinetic parameters as K(m)(Xu) = 24 +/- 3 mum and k(cat) = 35 +/- 5 s(-1). Crystal structures were determined for hXK, on its own and in complexes with Xu, ADP, and a fluorinated inhibitor. These reveal that hXK has a two-domain fold characteristic of the sugar kinase/hsp70/actin superfamily, with glycerol kinase as its closest relative. Xu binds to domain-I and ADP to domain-II, but in this open form of hXK they are 10 A apart, implying that a large scale conformational change is required for catalysis. Xu binds in its linear keto-form, sandwiched between a Trp side chain and polar side chains that provide exquisite hydrogen bonding recognition. The hXK structure provides a basis for the design of specific inhibitors with which to probe its roles in sugar metabolism and metabolic disease. |
