scholarly journals Evidence that Asn542 of neprilysin (EC 3.4.24.11) is involved in binding of the P2′ residue of substrates and inhibitors

1995 ◽  
Vol 311 (2) ◽  
pp. 623-627 ◽  
Author(s):  
N Dion ◽  
H Le Moual ◽  
M C Fournié-Zaluski ◽  
B P Roques ◽  
P Crine ◽  
...  
Keyword(s):  
Active Site ◽  
Substrate Binding ◽  
Biologically Active ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Active Site Residues ◽  
Hydrophobic Cluster Analysis ◽  
Active Peptides ◽  
Ic50 Values

Neprilysin (EC 3.4.24.11) is a Zn2+ metallopeptidase involved in the degradation of biologically active peptides, e.g. enkephalins and atrial natriuretic peptide. The substrate specificity and catalytic activity of neprilysin resemble those of thermolysin, a crystallized bacterial Zn2+ metalloprotease. Despite little overall homology between the primary structures of thermolysin and neprilysin, many of the amino acid residues involved in catalysis, as well as Zn2+ and substrate binding, are highly conserved. Most of the active-site residues of neprilysin have their homologues in thermolysin and have been characterized by site-directed mutagenesis. Furthermore, hydrophobic cluster analysis has revealed some other analogies between the neprilysin and thermolysin sequences [Benchetrit, Bissery, Mornon, Devault, Crine and Roques (1988) Biochemistry 27, 592-596]. According to this analysis the role of Asn542 in the neprilysin active site is analogous to that of Asn112 of thermolysin, which is to bind the substrate. Site-directed mutagenesis was used to change Asn542 to Gly or Gln residues. The effect of these mutations on substrate catalysis and inhibitor binding was examined with a series of thiorphan-like compounds containing various degrees of methylation at the P2′ residue. For both mutated enzymes, determination of kinetic parameters with [D-Ala2,Leu5]enkephalin as substrate showed that the large decrease in activity was attributable to an increase in Km (14-16-fold) whereas kcat values were only slightly affected (2-3-fold decrease). This is in agreement with Asn542 being involved in substrate binding rather than directly in catalysis. Finally, the IC50 values for thiorphan and substituted thiorphans strongly suggest that Asn542 of neprilysin binds the substrate on the amino side of the P2′ residue by formation of a unique hydrogen bond.

scholarly journals Site-directed mutagenesis identified the key active site residues of alcohol acyltransferase PpAAT1 responsible for aroma biosynthesis in peach fruits

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Zhi-Zhong Song ◽  
Bin Peng ◽  
Zi-Xia Gu ◽  
Mei-Ling Tang ◽  
Bei Li ◽  
...  
Keyword(s):  
Amino Acid ◽  
Enzymatic Activity ◽  
Amino Acid Residue ◽  
Active Site ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Active Site Residues ◽  
Peach Fruit ◽  
Alcohol Acyltransferase

AbstractThe aroma of peach fruit is predominantly determined by the accumulation of γ-decalactone and ester compounds. A previous study showed that the biosynthesis of these aroma compounds in peach fruit is catalyzed by PpAAT1, an alcohol acyltransferase. In this work, we investigated the key active site residues responsible for γ-decalactone and ester biosynthesis. A total of 14 candidate amino acid residues possibly involved in internal esterification and 9 candidate amino acid residues possibly involved in esterification of PpAAT1 were assessed via site-directed mutagenesis. Analyses of the in vitro enzyme activities of PpAAT1 and its site-directed mutant proteins (PpAAT1-SMs) with different amino acid residue mutations as well as the contents of γ-decalactone in transgenic tobacco leaves and peach fruits transiently expressing PpAAT1 and PpAAT1-SMs revealed that site-directed mutation of H165 in the conserved HxxxD motif led to lost enzymatic activity of PpAAT1 in both internal esterification and its reactions, whereas mutation of the key amino acid residue D376 led to the total loss of γ-decalactone biosynthesis activity of PpAAT1. Mutations of 9 and 7 other amino acid residues also dramatically affected the enzymatic activity of PpAAT1 in the internal esterification and esterification reactions, respectively. Our findings provide a biochemical foundation for the mechanical biosynthesis of γ-decalactone and ester compounds catalyzed by PpAAT1 in peach fruits, which could be used to guide the molecular breeding of new peach species with more favorable aromas for consumers.

Chitosanase from Streptomyces sp. strain N174: a comparative review of its structure and function

1997 ◽  
Vol 75 (6) ◽  
pp. 687-696 ◽  
Author(s):  
Tamo Fukamizo ◽  
Ryszard Brzezinski
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Substrate Binding ◽  
Structure And Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Streptomyces Sp ◽  
Binding Cleft ◽  
And Function

Novel information on the structure and function of chitosanase, which hydrolyzes the beta -1,4-glycosidic linkage of chitosan, has accumulated in recent years. The cloning of the chitosanase gene from Streptomyces sp. strain N174 and the establishment of an efficient expression system using Streptomyces lividans TK24 have contributed to these advances. Amino acid sequence comparisons of the chitosanases that have been sequenced to date revealed a significant homology in the N-terminal module. From energy minimization based on the X-ray crystal structure of Streptomyces sp. strain N174 chitosanase, the substrate binding cleft of this enzyme was estimated to be composed of six monosaccharide binding subsites. The hydrolytic reaction takes place at the center of the binding cleft with an inverting mechanism. Site-directed mutagenesis of the carboxylic amino acid residues that are conserved revealed that Glu-22 and Asp-40 are the catalytic residues. The tryptophan residues in the chitosanase do not participate directly in the substrate binding but stabilize the protein structure by interacting with hydrophobic and carboxylic side chains of the other amino acid residues. Structural and functional similarities were found between chitosanase, barley chitinase, bacteriophage T4 lysozyme, and goose egg white lysozyme, even though these proteins share no sequence similarities. This information can be helpful for the design of new chitinolytic enzymes that can be applied to carbohydrate engineering, biological control of phytopathogens, and other fields including chitinous polysaccharide degradation. Key words: chitosanase, amino acid sequence, overexpression system, reaction mechanism, site-directed mutagenesis.

scholarly journals Domain sliding of two Staphylococcus aureus N-acetylglucosaminidases enables their substrate-binding prior to its catalysis

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Sara Pintar ◽  
Jure Borišek ◽  
Aleksandra Usenik ◽  
Andrej Perdih ◽  
Dušan Turk
Keyword(s):  
Crystal Structures ◽  
Active Site ◽  
Drug Targets ◽  
Substrate Binding ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Human Pathogen ◽  
Active Site Cleft ◽  
Novel Drug ◽  
Novel Drug Targets

AbstractTo achieve productive binding, enzymes and substrates must align their geometries to complement each other along an entire substrate binding site, which may require enzyme flexibility. In pursuit of novel drug targets for the human pathogen S. aureus, we studied peptidoglycan N-acetylglucosaminidases, whose structures are composed of two domains forming a V-shaped active site cleft. Combined insights from crystal structures supported by site-directed mutagenesis, modeling, and molecular dynamics enabled us to elucidate the substrate binding mechanism of SagB and AtlA-gl. This mechanism requires domain sliding from the open form observed in their crystal structures, leading to polysaccharide substrate binding in the closed form, which can enzymatically process the bound substrate. We suggest that these two hydrolases must exhibit unusual extents of flexibility to cleave the rigid structure of a bacterial cell wall.

scholarly journals Identification of the catalytic residues of the first family of β(1–3)glucanosyltransferases identified in fungi

2000 ◽  
Vol 347 (3) ◽  
pp. 741-747 ◽  
Author(s):  
Isabelle MOUYNA ◽  
Michel MONOD ◽  
Thierry FONTAINE ◽  
Bernard HENRISSAT ◽  
Barbara LÉCHENNE ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Active Site ◽  
Biochemical Analysis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Sequence Comparisons ◽  
Catalytic Residues ◽  
Hydrophobic Cluster Analysis ◽  
Hydrophobic Cluster ◽  
New Family

A new family of glycosylphosphatidylinositol-anchored β(1-3)glucanosyltransferases (Gelp), recently identified and characterized in the filamentous fungus Aspergillus fumigatus, showed functional similarity to the Gas/Phr/Epd protein families, which are involved in yeast morphogenesis. Sequence comparisons and hydrophobic cluster analysis (HCA) showed that all the Gas/Phr/Epd/Gel proteins belong to a new family of glycosylhydrolases, family 72. We confirmed by site-directed mutagenesis and biochemical analysis that the two conserved glutamate residues (the putative catalytic residues of this family, as determined by HCA) are involved in the active site of this family of glycosylhydrolases.

scholarly journals Site-directed mutagenesis of active site residues in a class I endochitinase from chestnut seeds

Glycobiology ◽  
1998 ◽  
Vol 8 (10) ◽  
pp. 1021-1028 ◽  
Author(s):  
G. Garcia-Casado ◽  
C. Collada ◽  
I. Allona ◽  
R. Casado ◽  
L. F. Pacios ◽  
...  
Keyword(s):  
Active Site ◽  
Site Directed Mutagenesis ◽  
Class I ◽  
Directed Mutagenesis ◽  
Active Site Residues
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