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<p>The hyperthermophilic enzyme, PfuAmyGT (PF0272), is a 656 residues-long, homodimeric GH57 glycoside hydrolase from <i>Pyrococcus furiosus</i>. It is a homolog of TLGT, an enzyme of known structure from <i>Thermococcus litoralis</i>, which is thought to contain two C-terminal domains of unknown function (DUFs), and a catalytic N-terminal domain. Results presented here suggest that PfuAmyGT is designed by nature to (A) act upon long-chain malto-oligosaccharides (e.g., starch/amylose) more efficiently than upon short-chain malto-oligosaccharides (e.g., maltotriose), (B) convert malto-oligosaccharide chains into identical pools of small malto-oligosaccharides and glucose, through the coupling of exo-amylase and disproportionating glucanotransferase functions, (C) use overlapping and proximal, but different (cooperating) sub-sites for the binding of donor and acceptor chains, (D) act upon donor chains passing through a tunnel, to progressively reduce the chain down to the length of maltose through processive exo-amylase action, (E) facilitate the cycling of acceptor chains that bind to the DUF domains, receive an excised glucose, and dissociate, (F) facilitate excised glucose to be transferred to water if there is no waiting acceptor, and (G) utilize four, rather than two, catalytic acidic residues (E131, D222, E224, and D362).</p> Graphical Abstract <p>The enzyme, PfuAmyGT, accepting donor malto-oligosaccharides at site D, and transferring glucose from donor termini to mono-, di- or oligo-maltosaccharides bound at site A. Acceptor substates at site A are recycled after each transfer; donor substrates at site D are replaced only when reduced to a length shorter than maltotriose.</p> <p></p>

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Transformation of Starch into an Equilibrium Pool of Glucose and Small Maltosaccharides by a Hyperthermophilic Enzyme Exhibiting Coupled (Exo)Amylase-Glucanotransferase Functions

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Arpita Sarkar,
  • Pallavi Kaila,
  • Prince Tiwari,
  • Purnananda Guptasarma

摘要

The hyperthermophilic enzyme, PfuAmyGT (PF0272), is a 656 residues-long, homodimeric GH57 glycoside hydrolase from Pyrococcus furiosus. It is a homolog of TLGT, an enzyme of known structure from Thermococcus litoralis, which is thought to contain two C-terminal domains of unknown function (DUFs), and a catalytic N-terminal domain. Results presented here suggest that PfuAmyGT is designed by nature to (A) act upon long-chain malto-oligosaccharides (e.g., starch/amylose) more efficiently than upon short-chain malto-oligosaccharides (e.g., maltotriose), (B) convert malto-oligosaccharide chains into identical pools of small malto-oligosaccharides and glucose, through the coupling of exo-amylase and disproportionating glucanotransferase functions, (C) use overlapping and proximal, but different (cooperating) sub-sites for the binding of donor and acceptor chains, (D) act upon donor chains passing through a tunnel, to progressively reduce the chain down to the length of maltose through processive exo-amylase action, (E) facilitate the cycling of acceptor chains that bind to the DUF domains, receive an excised glucose, and dissociate, (F) facilitate excised glucose to be transferred to water if there is no waiting acceptor, and (G) utilize four, rather than two, catalytic acidic residues (E131, D222, E224, and D362).

Graphical Abstract

The enzyme, PfuAmyGT, accepting donor malto-oligosaccharides at site D, and transferring glucose from donor termini to mono-, di- or oligo-maltosaccharides bound at site A. Acceptor substates at site A are recycled after each transfer; donor substrates at site D are replaced only when reduced to a length shorter than maltotriose.