Extremophilic SHMTs: From Structure to Biotechnology

Abstract

Recent advances in molecular and structural biology have improved the availability of virtually any biocatalyst in large quantity and have also provided an insight into the detailed structure-function relationships of many of them. These results allowed the rational exploitation of biocatalysts for use in organic synthesis. In this context, extremophilic enzymes are extensively studied for their potential interest for many biotechnological and industrial applications, as they offer increased rates of reactions, higher substrate solubility, and/or longer enzyme half-lives at the conditions of industrial processes. Serine hydroxymethyltransferase (SHMT), for its ubiquitous nature, represents a suitable model for analyzing enzyme adaptation to extreme environments. In fact, many SHMT sequences from Eukarya, Eubacteria and Archaea are available in data banks as well as several crystal structures. In addition, SHMT is structurally conserved because of its critical metabolic role; consequently, very few structural changes have occurred during evolution. Our research group analyzed the molecular basis of SHMT adaptation to high and low temperatures, using experimental and comparative in silico approaches. These structural and functional studies of SHMTs purified from extremophilic organisms can help to understand the peculiarities of the enzyme activity at extreme temperatures, indicating possible strategies for rational enzyme engineering.

Structural stability of cold-adapted serine hydroxymethyltransferase, a tool for β-hydroxy-α-amino acid biosynthesis

“…Such processes would certainly benefit from the use of SHMT that functions at low temperature [40]. Generally, psychrophilic enzymes provide important benefits through energy savings: they exhibit increased reaction yields in cold environments, a high level of stereospecificity [41], an increased thermal lability for rapid and easy enzyme inactivation when required and minimization of undesirable chemical reactions that can occur at higher temperatures.…”

The crystal structure of archaeal serine hydroxymethyltransferase reveals idiosyncratic features likely required to withstand high temperatures

“…As CC bond formation and cleavage reactions are at the heart of organic synthesis, SHMT enzymes are used in several biotechnological applications such as the synthesis of optically active β‐hydroxy‐α,ω‐diamino acid derivatives . The wealth of available information concerning the biochemical and structural properties of SHMTs from different sources, combined with enzyme modification by rational protein engineering, can be exploited to improve catalytic and physical properties and develop novel catalytic functions …”

“…7,8 The wealth of available information concerning the biochemical and structural properties of SHMTs from different sources, combined with enzyme modification by rational protein engineering, can be exploited to improve catalytic and physical properties and develop novel catalytic functions. 9 To date, three-dimensional (3D) structures have been experimentally determined only for SHMTs from eubacterial and eukaryotic organisms (Supporting Information Table S1). These structures display a highly conserved overall fold, with monomers organized into obligate homodimers (in eukarya the enzyme occurs as dimer of dimers).…”

Kinetic Mechanism and the Rate-limiting Step of Plasmodium vivax Serine Hydroxymethyltransferase

“…Although the reaction of SHMT from various species has been investigated, many of these studies focused on the nonphysiological reaction, or the reverse reaction of glycine and CH 2 -H 4 folate (2,7,8,17,18). The pre-steady-state kinetics of the H 4 folate-dependent SHMT reaction has never been investigated.…”