Crystallization and structure elucidation of GDSL esterase of Photobacterium sp. J15

The synthesis of cinnamyl acetate and deacetyl-7-aminocephalosporanic acid by a GDSL-type esterase and its substrate specificity analysis

GDSL-type esterases are promising biocatalysts for the food and pharmaceutical industries. Here, a GDSL-type esterase from Aspergillus niger CCTCC No. M2012538 (INANE1) was expressed and purified in Pichia pastoris GS115, and its catalytic performances were evaluated, including the synthesis of cinnamyl acetate and deacetyl-7-aminocephalosporanic acid (D-7-ACA). In addition, molecular docking and molecular dynamics simulations analyzed INANE1's substrate specificity. The substrate specificity profile indicated the recombinant esterase (rINANE1) was an acetylesterase with high specificity for p-nitrophenyl acetate (p-NPA). The rINANE1 exhibited maximum activity at pH 8.0 and 35 °C, where Km and Vmax were calculated as 0.13±0.03 mM and 22.56 ± 0.32 μmoL/min/mg, respectively. The yield of cinnamyl acetate of about 85 % was achieved in 24 h. The conversion rate of 7-aminocephalosporanic acid (7-ACA) could reach 92.71 ± 1.78 % at 25 °C and 2.5 h. Moreover, the INANE1 structure model, molecular docking, and molecular dynamics simulation demonstrated that the pocket of the catalytic triad Ser34, Asn267, and His270 could only accommodate p-NPA. INANE1 may be the first fungi esterase with cinnamyl acetate synthetic activity and 7-ACA hydrolysis activity. Therefore, INANE1 would be a promising enzyme with industrial values.

Unraveling the potential of uninvestigated thermoalkaliphilic lipases by molecular docking and molecular dynamic simulation: an in silico characterization study

Thermoalkaliphilic lipase enzymes are mostly favored for use in the detergent industry. While there has been considerable research on Geobacillus lipases, a significant portion of these enzymes remains unexplored or undocumented in the scientific literature. This work performed in silico phylogeny, sequence alignment, structural and enzyme-substrate interaction analyses of the five thermoalkaliphilic lipases belonging to different Geobacillus species (Geobacillus stearothermophilus lipase = GsLip, Geobacillus sp. B4113_201601 lipase = Gb4Lip, Geobacillus kaustophilus HTA426 lipase = GkLip, Geobacillus sp. SP22 lipase = GspLip, Geobacillus sp. NTU 03 lipase = GntLip). For this purpose, unreviewed enzyme sequences of five Geobacillus thermoalkaliphilic lipases were analyzed at sequence and phylogeny levels. 3D homology enzyme models were built, validated, and investigated by different bioinformatics tools. The ligand interactions screening using seven para-nitrophenyl (pNP) esters and enzyme-ligand interactions were analyzed on Gb4Lip:pNP-C12 and BTL2:pNP-C12 by MD simulation. Biophysicochemical characteristic analysis showed that Gb4Lip had a theoretical T m value of above 65 ºC, and a higher aliphatic index indicating greater thermal stability. Sequence alignment showed a hydrophilic threonine in the α6 helix of Gb4Lip, indicating high enzymatic activity. A normalized temperature factor B (B'-factor) analysis showed that the lid domains of five lipases significantly possessed lower B'-factor values, compared to G. thermocatenulatus lipase 2 (BTL2), indicating that they had higher rigidity. Molecular docking results indicated that the five lipases had the highest binding affinity toward pNP-C12. The RMSF investigation revealed that the thermostability of Gb4Lip is influenced by specific molecular elements: D202-S203 within the αB region of the lid domain, and E274-Q275 within the b3 strand, as well as W278 in the b3-b4 loop, and H282 in the b4 strand of the Ca2+-binding region. MD simulation analysis showed that catalytic residue S114 and at least one oxyanion hole residue (F17 and/or Q114) in Gb4Lip frequently formed hydrogen bonds with the pNP-C12 ligand at 343 K and 348 K throughout the simulation process, indicating that Gb4Lip might catalyze relatively long-chain ligand pNP-C12 with high performance. In conclusion, Gb4Lip might be a more suitable candidate as the detergent additive. In addition, this investigation can offer valuable perspectives on Family I.5 lipases such as Gb4Lip for future exploration in the field of protein engineering.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04023-5.

X-ray crystallography of mutant GDSL esterase S12A of Photobacterium marinum J15

GDSL esterase is designated as a member of Family II of lipolytic enzymes known to catalyse the synthesis and hydrolysis of ester bonds. The enzyme possesses a highly conserved motif Ser-Gly-Asn-His in the four conserved blocks I, II, III and V respectively. The enzyme characteristics, such as region-, chemo-, and enantioselectivity, help in resolving the racemic mixture of single-isomer chiral drugs. Recently, crystal structure of GDSL esterase from Photobacterium J15 has been reported (PDB ID: 5XTU) but not in complex with substrate. Therefore, GDSL in complex with substrate could provide insights into the binding mode of substrate towards inactive form of GDSL esterase (S12A) and identify the hot spot residues for the designing of a better binding pocket. Insight into molecular mechanisms is limited due to the lack of crystal structure of GDSL esterase-substrate complex. In this paper, the crystallization of mutant GDSL esterase (S12A) (PDB ID: 8HWO) and its complex with butyric acid (PDB ID: 8HWP) are reported. The optimized structure would be vital in determining hot spot residue for GDSL esterase. This preliminary study provides an understanding of the interactions between enzymes and hydrolysed p-nitro-phenyl butyrate. The information could guide in the rational design of GDSL esterase in overcoming the medical limitations associated with racemic mixture.

PTCL1-EstA from Paenarthrobacter aurescens TC1, a Candidate for Industrial Application Belonging to the VIII Esterase Family

The esterase PTCL1-EstA from Paenarthrobacter aurescens TC1 was expressed in Escherichia coli and characterized. An 1152 bp open reading frame encoding a 383 amino acid polypeptide was successfully expressed, the C-terminally His6-tagged PTCL1-EstA enzyme was purified, and the predicted molecular mass of the purified PTCL1-EstA was 40.6 kDa. The EstA family serine hydrolase PTCL1-EstA belongs to the esterase family VIII, contains esterase-labeled S-C-S-K sequences, and homologous class C beta-lactamase sequences. PTCL1-EstA favored p-nitrophenyl esters with C2-C6 chain lengths, but it was also able to hydrolyze long-chain p-nitrophenyl esters. Homology modelling and substrate docking predicted that Ser59 was an active site residue in PTCL1-EstA, as well as Tyr148, Ala325, and Asp323, which are critical in catalyzing the enzymatic reaction of p-nitrophenyl esters. PTCL1-EstA reached the highest specific activity against p-nitrophenyl butyrate (C4) at pH 7.0 and 45 °C but revealed better thermal stability at 40 °C and maintained high relative enzymatic activity and stability at pH 5.0–9.0. Fermentation medium optimization for PTCL1-EstA increased the enzyme activity to 510.76 U/mL, tapping the potential of PTCL1-EstA for industrial production.

Identification and Biochemical Characterization of a Novel Hormone-Sensitive Lipase Family Esterase Est19 from the Antarctic Bacterium Pseudomonas sp. E2-15

Esterases represent an important class of enzymes with a wide variety of industrial applications. A novel hormone-sensitive lipase (HSL) family esterase, Est19, from the Antarctic bacterium Pseudomonas sp. E2-15 is identified, cloned, and expressed. The enzyme possesses a GESAG motif containing an active serine (S) located within a highly conserved catalytic triad of Ser155, Asp253, and His282 residues. The catalytic efficiency (kcat/Km) of Est19 for the pNPC6 substrate is 148.68 s-1mM-1 at 40 °C. Replacing Glu154 juxtaposed to the critical catalytic serine with Asp (E154→D substitution) reduced the activity and catalytic efficiency of the enzyme two-fold, with little change in the substrate affinity. The wild-type enzyme retained near complete activity over a temperature range of 10-60 °C, while ~50% of its activity was retained at 0 °C. A phylogenetic analysis suggested that Est19 and its homologs may represent a new subfamily of HSL. The thermal stability and stereo-specificity suggest that the Est19 esterase may be useful for cold and chiral catalyses.

Structure elucidation and docking analysis of 5M mutant of T1 lipase Geobacillus zalihae

5M mutant lipase was derived through cumulative mutagenesis of amino acid residues (D43E/T118N/E226D/E250L/N304E) of T1 lipase from Geobacillus zalihae. A previous study revealed that cumulative mutations in 5M mutant lipase resulted in decreased thermostability compared to wild-type T1 lipase. Multiple amino acids substitution might cause structural destabilization due to negative cooperation. Hence, the three-dimensional structure of 5M mutant lipase was elucidated to determine the evolution in structural elements caused by amino acids substitution. A suitable crystal for X-ray diffraction was obtained from an optimized formulation containing 0.5 M sodium cacodylate trihydrate, 0.4 M sodium citrate tribasic pH 6.4 and 0.2 M sodium chloride with 2.5 mg/mL protein concentration. The three-dimensional structure of 5M mutant lipase was solved at 2.64 Å with two molecules per asymmetric unit. The detailed analysis of the structure revealed that there was a decrease in the number of molecular interactions, including hydrogen bonds and ion interactions, which are important in maintaining the stability of lipase. This study facilitates understanding of and highlights the importance of hydrogen bonds and ion interactions towards protein stability. Substrate specificity and docking analysis on the open structure of 5M mutant lipase revealed changes in substrate preference. The molecular dynamics simulation of 5M-substrates complexes validated the substrate preference of 5M lipase towards long-chain p-nitrophenyl-esters.

CE16 acetylesterases: in silico analysis, catalytic machinery prediction and comparison with related SGNH hydrolases

Bioinformatics analysis was focused on unique acetylesterases annotated in the CAZy database within the CE16 family and simultaneously belonging to the SGNH hydrolase superfamily. The CE16 acetylesterases were compared to structurally related SGNH hydrolases: (i) selected members of the CE2, CE3, CE6, CE12 and CE17 family of the CAZy database and (ii) structural representatives of the Lipase_GDSL and Lipase_GDSL_2 families according to the Pfam database. Sequence alignment based on four conserved sequence regions (CSRs) containing active-site residues was used to calculate sequence logos specific for each CE family and to construct a phylogenetic tree. In many members of the CE16 family, aspartic acid from the Ser-His-Asp catalytic triad has been replaced by asparagine, and based on structure-sequence comparison, an alternative catalytic dyad mechanism was predicted for these enzymes. In addition to four conserved regions, CSR-I, CSR-II, CSR-III and CSR-V, containing catalytic and oxyanion-hole residues, CSR-IV was found in the CE16 family as the only CAZy family. Tertiary structures of the characterized CE16 members prepared by homology modeling showed that the α/β/α sandwich fold as well as the topology of their active sites are preserved. The phylogenetic tree and sequence alignment indicate the existence of a subfamily in the CE16 family fully consistent with the known biochemical data. In addition, nonstandard CE16 members that differ from others were analyzed and their active-site residues were predicted. A better understanding of the structure-function relationship of acetylesterases can help in the targeted design of these enzymes for biotechnology.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-020-02575-w.

Structural insights into the putative bacterial acetylcholinesterase ChoE and its substrate inhibition mechanism

Mammalian acetylcholinesterase (AChE) is well-studied, being important in both cholinergic brain synapses and the peripheral nervous systems and also a key drug target for many diseases. In contrast, little is known about the structures and molecular mechanism of prokaryotic acetylcholinesterases. We report here the structural and biochemical characterization of ChoE, a putative bacterial acetylcholinesterase from Pseudomonas aeruginosa Analysis of WT and mutant strains indicated that ChoE is indispensable for P. aeruginosa growth with acetylcholine as the sole carbon and nitrogen source. The crystal structure of ChoE at 1.35 Å resolution revealed that this enzyme adopts a typical fold of the SGNH hydrolase family. Although ChoE and eukaryotic AChEs catalyze the same reaction, their overall structures bear no similarities constituting an interesting example of convergent evolution. Among Ser-38, Asp-285, and His-288 of the catalytic triad residues, only Asp-285 was not essential for ChoE activity. Combined with kinetic analyses of WT and mutant proteins, multiple crystal structures of ChoE complexed with substrates, products, or reaction intermediate revealed the structural determinants for substrate recognition, snapshots of the various catalytic steps, and the molecular basis of substrate inhibition at high substrate concentrations. Our results indicate that substrate inhibition in ChoE is due to acetate release being blocked by the binding of a substrate molecule in a nonproductive mode. Because of the distinct overall folds and significant differences of the active site between ChoE and eukaryotic AChEs, these structures will serve as a prototype for other prokaryotic acetylcholinesterases.

Genomic and phenomic analysis of a marine bacterium, Photobacterium marinum J15

Photobacterium species are widely distributed in the marine environment. The overall metabolism of this genus remains largely unknown. In order to improve our knowledge on this bacterium, the relationship between the genome and phenome of the Photobacterium isolate was analyzed. The cream colored, Gram-negative, rod-shaped and motile bacterial strain, J15, was isolated from marine water of Tanjung Pelepas, Johor, Malaysia. The 5,684,538 bp genome of strain J15 comprised 3 contigs (2 chromosomes and 1 plasmid) with G + C content of 46.39 % and contained 4924 protein-coding genes including 180 tRNAs and 40 rRNAs. The phenotypic microarray (PM) as analyzed using BIOLOG showed the utilization of; i) 93 of the 190 carbon sources tested, where 61 compounds were used efficiently; ii) 41 of the 95 nitrogen sources tested, where 22 compounds were used efficiently; and iii) 3 of the 94 phosphorous and sulphur sources tested. Furthermore, high tolerance to osmotic stress, basic pH and toxic compounds as well as resistance to antibiotics of strain J15 were determined by BIOLOG PM. The ANI and kSNP analyses revealed that strain J15 to be the same species with Photobacterium marinum AK15 with ANI value of 96.93 % and bootstrapping value of 100 in kSNP. Based on the ANI and kSNP analyses, strain J15 was identified as P. marinum J15.