Further improvement of phosphite dehydrogenase thermostability by saturation mutagenesis.


Phosphite dehydrogenase represents a new enzymatic system for regenerating reduced nicotinamide cofactors for industrial biocatalysis. We previously engineered a variant of phosphite dehydrogenase with relaxed cofactor specificity and significantly increased activity and stability. Here we performed one round of random mutagenesis followed by comprehensive saturation mutagenesis to further improve the enzyme thermostability while maintaining its activity. Two new thermostabilizing mutations were identified. These, along with the 12 mutations previously identified, were subjected to saturation mutagenesis using the parent enzyme or the engineered thermostable variant 12x as a template, followed by screening of variants with increased thermostability. Of the 12 previously identified sites, 6 yielded new variants with improved stability over the parent enzyme. Several mutations were found to be context-dependent. On the basis of molecular modeling and biochemical analysis, various mechanisms of thermostabilization were identified. Combining the most thermostabilizing mutation at each site resulted in a variant that showed a 100-fold increase in half-life at 62 degrees C over the 12x mutant. The final mutant has improved the half-life of thermal inactivation at 45 degrees C by 23,000-fold over the parent enzyme. The engineered phosphite dehydrogenase will be useful in NAD(P)H regeneration.

Submission Details

ID: oBQX3hYz

Submitter: Shu-Ching Ou

Submission Date: Aug. 24, 2018, 4:12 p.m.

Version: 1

Publication Details
McLachlan MJ;Johannes TW;Zhao H,Biotechnol Bioeng (2008) Further improvement of phosphite dehydrogenase thermostability by saturation mutagenesis. PMID:17615560
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant PDB Entries

Structure ID Release Date Resolution Structure Title
4E5K 2012-03-14T00:00:00+0000 1.95 Thermostable phosphite dehydrogenase in complex with NAD and sulfite
4E5M 2012-03-14T00:00:00+0000 1.85 Thermostable phosphite dehydrogenase E175A/A176R in complex with NADP
4E5N 2012-03-14T00:00:00+0000 1.7 Thermostable phosphite dehydrogenase in complex with NAD
4E5P 2012-03-14T00:00:00+0000 1.9 Thermostable phosphite dehydrogenase A176R variant in complex with NAD
4EBF 2012-03-23T00:00:00+0000 2.3 SeMet thermostable phosphite dehydrogenase Glu175-Ala mutant
4NU5 2013-12-03T00:00:00+0000 2.35 Crystal Structure of PTDH R301A
4NU6 2013-12-03T00:00:00+0000 2.65 Crystal Structure of PTDH R301K

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Phosphonate dehydrogenase (NAD-dependent phosphite dehydrogenase) O69054 PTXD_PSEST