Maltodextrin phosphorylase

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Maltodextrin phosphorylase is a

allosteric effects on metabolism, however MalP exhibits no allosteric properties. It has a higher affinity for linear oligosaccharides than the related glycogen phosphorylase.[1]

Mechanism

Maltodextrin phosphorylase facilitates maltodextrin metabolism through phosphorolysis of nonreducing glucosyl residues in order to produce Glc1P. MalP has a higher affinity for short, linear α-1,4 linked glucose

simple sugars[3]

[(1→4)-α-D-glucosyl](n) + Pi ⇌ [(1→4)-α-D-glucosyl](n-1) + α-D-glucose-1-phosphate.[4]

Previous study of the

catalytic activity and kinetic properties of the MalP enzyme has revealed that it has different binding sites for the terminal glucose residue of the oligosaccharide and glucose-1-phosphate depending on whether its involvement is in the forward (phosphorylase) or reverse (synthesis) reaction.[2]
Though the maltodextrin phosphorylase enzyme is capable of catalysis in both directions in vitro, its physiologically favored direction is as a phosphorylase.

Structure

The maltodextrin phosphorylase

protomer contains one pyridoxal 5ʹ-phosphate cofactor in the active site, essential to catalytic activity.[5]

Application & Significance

No clinical significance of maltodextrin phosphorylase has been presently identified for use in humans; however, the enzyme may have biotechnological significance as it may allow for obtaining complex substrates for clinical research at less expense. Glc1P, a critical element to MalP’s phosphorolytic bioconversion process and a rather expensive chemical, can be enzymatically derived from dextrins or other starchy materials.[6]

Regulation

Maltodextrin phosphorylase readily catalyzes the reverse reaction of Glc1P plus oligosaccharide to yield an oligosaccharide lengthened by one glucose residue and liberation of

mammalian glycogen phosphorylase (GP) at the catalytic site. In comparison to the mammalian GP, MalP is a simpler enzyme. It is regulated neither by allosteric effectors nor phosphorylation and it is expressed in E. coli as a constitutively active enzyme.[1]

Crystal structures of oligosaccharide bound across the catalytic site in both the binary and the ternary MalP enzyme/substrate complexes reveal the importance of the conformational change in the oligosaccharide substrate in the formation of ternary complexes and provides support for the role of the 50-phosphate group of pyridoxal phosphate (PLP) in catalysis.[1]

References

  1. ^
    PMID 12217700
    .
  2. ^ a b "Maltodextrin phosphorylase". biocyc.org. Retrieved 10 December 2023.
  3. PMID 16321936
    .
  4. ^ "KEGG REACTION: R01821". www.genome.jp. Retrieved 2023-12-14.
  5. PMID 10677342
    .
  6. doi:10.1016/0141-0229(94)00055-V
    .
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