Catalytic flexibility of rice glycosyltransferase OsUGT91C1 for the production of palatable steviol glycosides

Nat Commun. 2021 Dec 2;12(1):7030. doi: 10.1038/s41467-021-27144-4.

Abstract

Steviol glycosides are the intensely sweet components of extracts from Stevia rebaudiana. These molecules comprise an invariant steviol aglycone decorated with variable glycans and could widely serve as a low-calorie sweetener. However, the most desirable steviol glycosides Reb D and Reb M, devoid of unpleasant aftertaste, are naturally produced only in trace amounts due to low levels of specific β (1-2) glucosylation in Stevia. Here, we report the biochemical and structural characterization of OsUGT91C1, a glycosyltransferase from Oryza sativa, which is efficient at catalyzing β (1-2) glucosylation. The enzyme's ability to bind steviol glycoside substrate in three modes underlies its flexibility to catalyze β (1-2) glucosylation in two distinct orientations as well as β (1-6) glucosylation. Guided by the structural insights, we engineer this enzyme to enhance the desirable β (1-2) glucosylation, eliminate β (1-6) glucosylation, and obtain a promising catalyst for the industrial production of naturally rare but palatable steviol glycosides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbohydrate Sequence
  • Catalytic Domain
  • Diterpenes, Kaurane / chemical synthesis*
  • Diterpenes, Kaurane / metabolism
  • Gene Expression
  • Glucose / chemistry
  • Glucose / metabolism
  • Glucosides / chemical synthesis*
  • Glucosides / metabolism
  • Glycosylation
  • Glycosyltransferases / chemistry*
  • Glycosyltransferases / genetics
  • Glycosyltransferases / metabolism
  • Humans
  • Kinetics
  • Models, Molecular
  • Oryza / chemistry
  • Oryza / enzymology*
  • Plant Proteins / chemistry*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Engineering / methods
  • Protein Interaction Domains and Motifs
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Stevia / chemistry
  • Stevia / enzymology
  • Substrate Specificity
  • Sweetening Agents / chemical synthesis*
  • Sweetening Agents / metabolism
  • Taste / physiology
  • Uridine Diphosphate Glucose / chemistry
  • Uridine Diphosphate Glucose / metabolism

Substances

  • Diterpenes, Kaurane
  • Glucosides
  • Plant Proteins
  • Recombinant Proteins
  • Sweetening Agents
  • stevioside
  • steviol
  • Glycosyltransferases
  • Glucose
  • Uridine Diphosphate Glucose