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Directed evolution of the fusion enzyme for improving astaxanthin biosynthesis in Saccharomyces cerevisiae.

ABSTRACT: The accumulation of the intermediate zeaxanthin and canthaxanthin in the astaxanthin biosynthesis pathway catalyzed by β-carotene hydroxylase (crtZ) and β-carotene ketolase (crtW) decreases the content of the astaxanthin. Here, we exploited directed evolution of the fusion of crtZ and crtW for improving astaxanthin biosynthesis in Saccharomyces cerevisiae. The results demonstrated that the fusion enzyme of crtZ-crtW with 2 X GGGGS peptides linker can effectively reduce the accumulation of intermediates and improves the content of astaxanthin. Compared with the control strain, the fusion enzyme of ketase and hydroxylase reduced zeaxanthin and canthaxanthin by 7 and 14 times and increased astaxanthin by 1.6 times, respectively. Moreover, 9 variant fusion mutants with improved astaxanthin production were generated through directed evolution. Combining these dominant mutants generated a variant, L95S + I206L, which increased the astaxanthin content of 3.8 times than the control strain. The AlphaFold2 assisted structural analysis indicated that these two mutations alter the interaction between the substrate and the enzymes pocket. Our research provided an efficient idea to reduce the accumulation of the intermediate products in complex biosynthesis pathway.

SUBMITTER: Ding YW

PROVIDER: S-EPMC9668533 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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Directed evolution of the fusion enzyme for improving astaxanthin biosynthesis in Saccharomyces cerevisiae.

Ding Yong-Wen YW Lu Chuan-Zhen CZ Zheng Yan Y Ma Han-Zhang HZ Jin Jin J Jia Bin B Yuan Ying-Jin YJ

Synthetic and systems biotechnology 20221110 1

The accumulation of the intermediate zeaxanthin and canthaxanthin in the astaxanthin biosynthesis pathway catalyzed by β-carotene hydroxylase (crtZ) and β-carotene ketolase (crtW) decreases the content of the astaxanthin. Here, we exploited directed evolution of the fusion of crtZ and crtW for improving astaxanthin biosynthesis in Saccharomyces cerevisiae. The results demonstrated that the fusion enzyme of crtZ-crtW with 2 X GGGGS peptides linker can eff ...[more]

PMID: 36408203

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Project description:Backgroundβ-glucosidases (BGLs) catalyze the hydrolysis of soluble cellodextrins to glucose and are a critical component of cellulase systems. In order to engineer Saccharomyces cerevisiae for the production of ethanol from cellulosic biomass, a BGL tailored to industrial bioconversions is needed.ResultsWe applied a directed evolution strategy to a glycosyl hydrolase family 3 (GH3) BGL from Aspergillus niger (BGL1) by expressing a library of mutated bgl1 genes in S. cerevisiae and used a two-step functional screen to identify improved enzymes. Twelve BGL variants that supported growth of S. cerevisiae on cellobiose and showed increased activity on the synthetic substrate p-nitrophenyl-β-D-glucopyranoside were identified and characterized. By performing kinetic experiments, we found that a Tyr → Cys substitution at position 305 of BGL1 dramatically reduced transglycosidation activity that causes inhibition of the hydrolytic reaction at high substrate concentrations. Targeted mutagenesis demonstrated that the position 305 residue is critical in GH3 BGLs and likely determines the extent to which transglycosidation reactions occur. We also found that a substitution at Gln(140) reduced the inhibitory effect of glucose and could be combined with the Y305C substitution to produce a BGL with decreased sensitivity to both the product and substrate. Using the crystal structure of a GH3 BGL from A. aculeatus, we mapped a group of beneficial mutations to the β/α domain of the molecule and postulate that this region modulates activity through subunit interactions. Six BGL variants were identified with substitutions in the MFα pre-sequence that was used to mediate secretion of the protein. Substitutions at Pro(21) or Val(22) of the MFα pre-sequence could produce up to a twofold increase in supernatant hydrolase activity and provides evidence that expression and/or secretion was an additional factor limiting hydrolytic activity.ConclusionsUsing directed evolution on BGL1, we identified a key residue that controls hydrolytic and transglycosidation reactions in GH3 BGLs. We also found that several beneficial mutations could be combined and increased the hydrolytic activity for both synthetic and natural substrates.

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Directed evolution of the fusion enzyme for improving astaxanthin biosynthesis in Saccharomyces cerevisiae.

Publications

Directed evolution of the fusion enzyme for improving astaxanthin biosynthesis in <i>Saccharomyces cerevisiae</i>.

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