The X-ray Crystal Structures of Human α-Phosphomannomutase 1 Reveal the Structural Basis of Congenital Disorder of Glycosylation Type 1a

Abstract

Congential disorder of glycosylation type 1a (CDG-1a) is a congenital disease characterized by severe defects in nervous system development. It is caused by mutations in ␣-phosphomannomutase (of which there are two isozymes, ␣-PMM1 and ␣-PPM2).

DFT investigation on the reaction mechanism catalyzed by α-phosphomannomutase1 in protonated/deprotonated states

“…Through interaction analysis, we know that Asp19 (−31.44 kcal mol −1 ), Gly53 (−5.21 kcal mol −1 ), Lys58 (−6.82 kcal mol −1 ), Gln62 (−6.92 kcal mol −1 ) and Arg132 (−6.11 kcal mol −1 ) are important anchoring residues for α-phosphomannomutase1 and have main contribution to D-mannose 6-phosphate interaction, and Asp19 and Gln62 are the important amino acids. The docking results are in good agreement with the experiment results by Sivaggi et al [12].…”

“…Sivaggi et al [12] reported that the active site of α-phosphomannomutase1, and based on the report, the binding pocket was constructed composed of 17 residues (Asp19, Asp21, Arg28, Gly53, Ser54, Lys58, Gln62, Arg132, Asn137, Pro140, Arg150, Ser188, Asp190, Lys198, Asn218, Glu219, Asn225). Sivaggi et al [12] also revealed once the substrate is bound with the α-phosphomannomutase1, there is presumably a change in the conformation of the hinge region that pushes the substrate into the active site as the cap binds to core domain, and binding of the substrate would mitigate the repulsion of the cap and core domains, favoring cap closure. The structure of complex α-phosphomannomutase1 and D-mannose 6-phosphate which obtained by docking is displayed in Fig.…”

“…The α-phosphomannomutase1 catalyzes the interconversion between D-mannose 6-phosphate and α-D-mannose1-phophate (the reaction catalyzed by α-phosphomannomutase1 shown in Scheme1) via a bisphosphorylated intermediate, and α-phosphomannomutase1 is required for GDP-mannose and dolichol-phosphate-mannose biosynthesis [11,12]. The α-phosphomannomutase1 belongs to the haloalkanoic acid dehalogenase superfamily (HADSF), distinguishing it in structurally and mechanistically from the phosphomanno/ phosphoglucomutase enzyme of the phosphohexomutase superfamily which are integral to glycolysis in both prokaryotes and eukaryotes [13], and are integral to alginate biosynthesis in Gram-negative bacteria [12,14].…”

“…The α-phosphomannomutase1 belongs to the haloalkanoic acid dehalogenase superfamily (HADSF), distinguishing it in structurally and mechanistically from the phosphomanno/ phosphoglucomutase enzyme of the phosphohexomutase superfamily which are integral to glycolysis in both prokaryotes and eukaryotes [13], and are integral to alginate biosynthesis in Gram-negative bacteria [12,14].…”

“…The intermediate must then reorient ∼180°to be in the position for second phosphoryl group transfers from the intermediate back to the enzyme. Silvaggi et al [12] reported the X-ray crystal structure of α-phosphomannomutase1 (PDB code 2FUC), revealed that the key active-site residue is catalytic nucleophile Asp19, and proposed the similar reaction mechanism for α-phosphomannomutase1: the interconversion of the α-D-mannose 1-phophate to D-mannose 6-phosphate via a mannose-1,6-(bis) phosphate intermediate generated by the α-phosphomannomutase1.…”