Correlation Analysis of Key Residue Sites between Computational-Aided Design Thermostability d-Amino Acid Oxidase and Ancestral Enzymes

The d-amino acid oxidase (DAAO) from Rhodotorula taiwanensis has proven to have great potential for applications due to its excellent catalytic kinetic parameters. However, its poor thermal stability has limited its performance in biocatalysis. Herein, starting from the variant SHVG of RtwDAAO, this study employed a comprehensive computational design approach for protein stability engineering, resulting in positive substitutions at specific sites (A43S, T45M, C234L, E195Y). The generated variant combination, SHVG/SMLY, exhibited a significant synergistic effect, leading to an extension of the half-life and Tmapp. The ancestral sequence reconstruction revealed the conservation of the variant sites. The association of the variant sites with the highly stable ancestral enzyme was further explored. After determining the contribution of the variant sites to thermal stability, it was applied to other homologous sequences and validated. Molecular dynamics simulations indicated that the increased hydrophobicity of the variant SHVG/SMLY was a key factor for the increased stability, with strengthened intersubunit interactions playing an important role. In addition, the physical properties of the amino acids themselves were identified as crucial factors for thermal stability generality in homologous enzymes, which is important for the rapid acquisition of a series of stable enzymes.

Crystal structure and molecular dynamics simulations of a promiscuous ancestor reveal residues and an epistatic interaction involved in substrate binding and catalysis in the ATP-dependent vitamin kinase family members

Enzymes with hydroxymethylpyrimidine/phosphomethylpyrimidine kinase activity (HMPPK) are essential in the vitamin B1 (thiamine pyrophosphate) biosynthesis and recycling pathways. In contrast, enzymes with pyridoxal kinase activity (PLK) produce pyridoxal phosphate (vitamin B6), an essential cofactor for various biochemical reactions. In the ATP-dependent vitamin kinases family, the members of PLK/HMPPK-like subfamily have both enzymatic activities. It has been proposed that the promiscuous PLK activity of ancestral HMPPK enzymes could have been the starting point for this activity. In earlier work, we reconstructed the ancestral sequences of this family and characterized the substrate specificity of the common ancestor between PLK/HMPPK-like and HMPPK enzymes (AncC). From these studies, the Gln45Met mutation was proposed as a critical event for the PLK activity emergence. Here, we crystallize and determine the AncC structure by X-ray crystallography and assess the role of the Gln45Met mutation by site-directed mutagenesis. Kinetic characterization of this mutant shows a significant increase in the PL affinity. Through molecular dynamics simulation and MM/PBSA calculations some residues, important for substrate interactions and catalysis, were identified in the wild type and in the mutated ancestor. Interestingly, a strong epistatic interaction responsible for the evolutionary pathway of the PLK activity in PLK/HMPPK-like enzymes was revealed. Also, other putative mutations relevant to PLK activity in modern PLK/HMPPK-like enzymes were identified.

FireProtASR: A Web Server for Fully Automated Ancestral Sequence Reconstruction

There is a great interest in increasing proteins’ stability to widen their usability in numerous biomedical and biotechnological applications. However, native proteins cannot usually withstand the harsh industrial environment, since they are evolved to function under mild conditions. Ancestral sequence reconstruction is a well-established method for deducing the evolutionary history of genes. Besides its applicability to discover the most probable evolutionary ancestors of the modern proteins, ancestral sequence reconstruction has proven to be a useful approach for the design of highly stable proteins. Recently, several computational tools were developed, which make the ancestral reconstruction algorithms accessible to the community, while leaving the most crucial steps of the preparation of the input data on users’ side. FireProt^ASR aims to overcome this obstacle by constructing a fully automated workflow, allowing even the unexperienced users to obtain ancestral sequences based on a sequence query as the only input. FireProt^ASR is complemented with an interactive, easy-to-use web interface and is freely available at https://loschmidt.chemi.muni.cz/fireprotasr/.

Increase of Redox Potential during the Evolution of Enzymes Degrading Recalcitrant Lignin

To investigate how ligninolytic peroxidases acquired the uniquely high redox potential they show today, their ancestors were resurrected and characterized. Unfortunately, the transient Compounds I (CI) and II (CII) from peroxide activation of the enzyme resting state (RS) are unstable. Therefore, the reduction potentials (E°') of the three redox couples (CI/RS, CI/CII and CII/RS) were estimated (for the first time in a ligninolytic peroxidase) from equilibrium concentrations analyzed by stopped-flow UV/Vis spectroscopy. Interestingly, the E°' of rate-limiting CII reduction to RS increased 70 mV from the common peroxidase ancestor to extant lignin peroxidase (LiP), and the same boost was observed for CI/RS and CI/CII, albeit with higher E°' values. A straightforward correlation was found between the E°' value and the progressive displacement of the proximal histidine Hϵ1 chemical shift in the NMR spectra, due to the higher paramagnetic effect of the heme Fe³⁺ . More interestingly, the E°' and NMR data also correlated with the evolutionary time, revealing that ancestral peroxidases increased their reduction potential in the evolution to LiP thanks to molecular rearrangements in their heme pocket during the last 400 million years.

Reconstructed ancestral enzymes reveal that negative selection drove the evolution of substrate specificity in ADP-dependent kinases

One central goal in molecular evolution is to pinpoint the mechanisms and evolutionary forces that cause an enzyme to change its substrate specificity; however, these processes remain largely unexplored. Using the glycolytic ADP-dependent kinases of archaea, including the orders Thermococcales, Methanosarcinales, and Methanococcales, as a model and employing an approach involving paleoenzymology, evolutionary statistics, and protein structural analysis, we could track changes in substrate specificity during ADP-dependent kinase evolution along with the structural determinants of these changes. To do so, we studied five key resurrected ancestral enzymes as well as their extant counterparts. We found that a major shift in function from a bifunctional ancestor that could phosphorylate either glucose or fructose 6-phosphate (fructose-6-P) as a substrate to a fructose 6-P-specific enzyme was started by a single amino acid substitution resulting in negative selection with a ground-state mode against glucose and a subsequent 1,600-fold change in specificity of the ancestral protein. This change rendered the residual phosphorylation of glucose a promiscuous and physiologically irrelevant activity, highlighting how promiscuity may be an evolutionary vestige of ancestral enzyme activities, which have been eliminated over time. We also could reconstruct the evolutionary history of substrate utilization by using an evolutionary model of discrete binary characters, indicating that substrate uses can be discretely lost or acquired during enzyme evolution. These findings exemplify how negative selection and subtle enzyme changes can lead to major evolutionary shifts in function, which can subsequently generate important adaptive advantages, for example, in improving glycolytic efficiency in Thermococcales.