New deblocking aminopeptidases from Pyrococcus horikoshii

How metal cofactors drive dimer-dodecamer transition of the M42 aminopeptidase TmPep1050 of Thermotoga maritima

The M42 aminopeptidases are dinuclear aminopeptidases displaying a peculiar tetrahedron-shaped structure with 12 subunits. Their quaternary structure results from the self-assembly of six dimers controlled by their divalent metal ion cofactors. The oligomeric-state transition remains debated despite the structural characterization of several archaeal M42 aminopeptidases. The main bottleneck is the lack of dimer structures, hindering the understanding of structural changes occurring during the oligomerization process. We present the first dimer structure of an M42 aminopeptidase, TmPep1050 of Thermotoga maritima, along with the dodecamer structure. The comparison of both structures has allowed us to describe how the metal ion cofactors modulate the active-site fold and, subsequently, affect the interaction interface between dimers. A mutational study shows that the M1 site strictly controls dodecamer formation. The dodecamer structure of TmPep1050 also reveals that a part of the dimerization domain delimits the catalytic pocket and could participate in substrate binding.

Characterization of thermostable deblocking aminopeptidases of archaeon Thermococcus onnurineus NA1 by proteomic and biochemical approaches

Thermococcus onnurineus NA1 is a hyperthermophilic archaeon that grows optimally at >80°C. The deblocking aminopeptidase (DAP) (TNA1-DAP1) encoded in Ton_1032 of T. onnurineus NA1 is considered a major DAP. However, four genes encoding putative DAP have been identified from a genomic analysis of T. onnurineus NA1. A proteomic analysis revealed that all four DAPs were differentially induced in YPS culture medium and, particularly, two DAPs (TNA1-DAP1 and TNA1-DAP2) were dominantly expressed in T. onnurineus NA1. The biochemical properties and enzyme activity of DAPs induced in an E. coli expression system suggested that the two major DAPs play complementary roles in T. onnurineus NA1.

Proteomic characterization of the sulfur-reducing hyperthermophilic archaeon Thermococcus onnurineus NA1 by 2-DE/MS-MS

Thermococcus onnurineus NA1, a sulfur-reducing hyperthermophilic archaeon, was isolated from a deep-sea hydrothermal vent area in Papua New Guinea. The strain requires elemental sulfur as a terminal electron acceptor for heterotrophic growth on peptides, amino acids and sugars. Recently, genome sequencing of Thermococcus onnurineus NA1 was completed. In this study, 2-DE/MS-MS analysis of the cytosolic proteome was performed to elucidate the metabolic characterization of Thermococcus onnurineus NA1 at the protein level. Among the 1,136 visualized protein spots, 110 proteins were identified. Enzymes related to metabolic pathways of amino acids utilization, glycolysis, pyruvate conversion, ATP synthesis, and protein synthesis were identified as abundant proteins, highlighting the fact that these are major metabolic pathways in Thermococcus onnurineus NA1. Interestingly, multiple spots of phosphoenolpyruvate synthetase and elongation factor Tu were found on 2D gels generated by truncation at the N-terminus, implicating the cellular regulatory mechanism of this key enzyme by protease degradation. In addition to the proteins involved in metabolic systems, we also identified various proteases and stress-related proteins. The proteomic characterization of abundantly induced proteins using 2-DE/MS-MS enables a better understanding of Thermococcus onnurineus NA1 metabolism.

Biochemical characterization of deblocking aminopeptidase from hyperthermophilic archaeon Thermococcus onnurineus NA1

A genomic analysis of the hyperthermophilic archaeon Thermoccoccus onnurineus NA1 (TNA1) revealed the presence of a deblocking aminopeptidase (DAP) gene with high similarity to the genes of DAPs from Pyrococcus furiosus (86%) and Pyrococcus horikoshii (83% identity). The optimum aminopeptidase activity of the recombinant enzyme was observed at pH 7.5 and in the range of 90 degrees C to 100 degrees C. The specific aminopeptidase and deblocking activities of the enzyme toward Leu-pNA and Ac-Leu-pNA were 18- and 3-fold higher than those of a P. horikoshii DAP (DAP2), respectively. The enzyme activity was significantly increased by Co(2+) ions. The presence of Co(2+) ions induced the activation of the enzyme with heating and changed the large oligomer to a dimer. The enzyme activated by Co(2+) ions appeared to eventually be inactivated by autodegradation, which was confirmed by mass spectrometry.

Hyperthermophilic enzymes − stability, activity and implementation strategies for high temperature applications

Current theories agree that there appears to be no unique feature responsible for the remarkable heat stability properties of hyperthermostable proteins. A concerted action of structural, dynamic and other physicochemical attributes are utilized to ensure the delicate balance between stability and functionality of proteins at high temperatures. We have thoroughly screened the literature for hyperthermostable enzymes with optimal temperatures exceeding 100 degrees C that can potentially be employed in multiple biotechnological and industrial applications and to substitute traditionally used, high-cost engineered mesophilic/thermophilic enzymes that operate at lower temperatures. Furthermore, we discuss general methods of enzyme immobilization and suggest specific strategies to improve thermal stability, activity and durability of hyperthermophilic enzymes.