2i65: Difference between revisions

[[Image:2i65.gif|left|200px]]<br /><applet load="2i65" size="350" color="white" frame="true" align="right" spinBox="true"  

The enzymatic cleavage of the nicotinamide-glycosidic bond on nicotinamide adenine dinucleotide (NAD(+)) has been proposed to go through an oxocarbenium ion-like transition state. Because of the instability of the ionic intermediate, there has been no structural report on such a transient reactive species. Human CD38 is an ectoenzyme that can use NAD(+) to synthesize two calcium-mobilizing molecules. By using NAD(+) and a surrogate substrate, NGD(+), we captured and determined crystal structures of the enzyme complexed with an intermediate, a substrate, and a product along the reaction pathway. Our results showed that the intermediate is stabilized by polar interactions with the catalytic residue Glu(226) rather than by a covalent linkage. The polar interactions between Glu(226) and the substrate 2',3'-OH groups are essential for initiating catalysis. Ser(193) was demonstrated to have a regulative role during catalysis and is likely to be involved in intermediate stabilization. In addition, a product inhibition effect by ADP-ribose (through the reorientation of the product) or GDP-ribose (through the formation of a covalently linked GDP-ribose dimer) was observed. These structural data provide insights into the understanding of multiple catalysis and clues for drug design.

2I65 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=NAD:'>NAD</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/NAD(+)_nucleosidase NAD(+) nucleosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.2.5 3.2.2.5] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2I65 OCA].  

[[Category: Kriksunov, I A.]]

[[Category: Lee, H C.]]

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