scholarly journals A glutamate residue contributes to the exopeptidase specificity in aminopeptidase A

1998 ◽  
Vol 334 (2) ◽  
pp. 407-413 ◽  
Author(s):  
Gilles VAZEUX ◽  
Xavier ITURRIOZ ◽  
Pierre CORVOL ◽  
Catherine LLORENS-CORTES
Keyword(s):  
Consensus Sequence ◽  
Kinetic Studies ◽  
Acetyl Derivative ◽  
Site Directed Mutagenesis ◽  
Inhibitory Potency ◽  
Zinc Metalloprotease ◽  
Fold Reduction ◽  
Membrane Bound ◽  
Aminopeptidase A

Aminopeptidase A (EC 3.4.11.7, APA) is a 130 kDa membrane-bound aminopeptidase that contains the consensus sequence HEXXH (385–389) found in the zinc metalloprotease family, the zincins. Sequence alignment of the mouse APA with other monozinc-aminopeptidases indicates the presence of a highly conserved glutamate residue (Glu352 in APA) found in the conserved motif GAMEN (349–353). In monozinc-aminopeptidases, the negative charge of the glutamate side-chain carboxylate may constitute the anionic binding site involved in the recognition of the free amino group of substrates or inhibitors. The functional role of Glu352 in APA was investigated by substituting this residue with an aspartate (Asp352), a glycine (Gly352), a glutamine (Gln352) or an arginine (Arg352) residue by site-directed mutagenesis. Kinetic studies showed that the Km values of the mutant enzymes were unaffected, whereas kcat values were decreased 10–250-fold, resulting in a 10-, 30- 260- and 400-fold reduction in cleavage efficiencies for the mutants Asp352, Gly352, Gln352 and Arg352 respectively. The inhibitory potency of two different classes of inhibitors, a thiol and a phosphonate compound, was significantly (P< 0.05) decreased by 10- and 4-fold respectively in the mutated enzymes. Moreover, the inhibitory potency of angiotensin I, used as a competitor of the synthetic substrate α-l-glutamyl β-naphthylamide, displayed a 4-fold reduction (P< 0.01) in the mutated enzymes, whereas the Ki values of its N-acetyl derivative were unchanged. These data strongly suggest that Glu352 is involved in the catalytic process of APA and contributes to the exopeptidase activity of this enzyme through interaction with the N-terminal part of substrates or inhibitors.

Probing the Role of Tyr 64 ofTreponema denticolaCystalysin by Site-Directed Mutagenesis and Kinetic Studies†

Biochemistry ◽  
2005 ◽  
Vol 44 (42) ◽  
pp. 13970-13980 ◽  
Author(s):  
Barbara Cellini ◽  
Mariarita Bertoldi ◽  
Riccardo Montioli ◽  
Carla Borri Voltattorni
Keyword(s):  
Kinetic Studies ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis

Mutagenesis of the borage Δ6 fatty acid desaturase

2000 ◽  
Vol 28 (6) ◽  
pp. 636-638 ◽  
Author(s):  
O. Sayanova ◽  
F. Beaudoin ◽  
B. Libisch ◽  
P. Shewry ◽  
J. Napier
Keyword(s):  
Fatty Acid ◽  
Consensus Sequence ◽  
Fatty Acid Desaturase ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
The Third ◽  
Membrane Bound ◽  
Fusion Domain ◽  
Δ6 Desaturase

The consensus sequence of the third histidine box of a range of Δ5, Δ6, Δ8 and sphingolipid desaturases differs from that of the membrane-bound non-fusion Δ12 and Δ15 desaturases in the presence of glutamine instead of histidine. We have used site-directed mutagenesis to determine the importance of glutamine and other residues of the third histidine box and created a chimaeric enzyme to determine the ability of the Cyt b5 fusion domain from the plant sphingolipid desaturase to substitute for the endogenous domain of the Δ6 desaturase.

scholarly journals A Conserved Histidine Is Essential for Glycerolipid Acyltransferase Catalysis

1998 ◽  
Vol 180 (6) ◽  
pp. 1425-1430 ◽  
Author(s):  
Richard J. Heath ◽  
Charles O. Rock
Keyword(s):  
Aspartic Acid ◽  
Acyl Carrier Protein ◽  
Site Directed Mutagenesis ◽  
Carrier Protein ◽  
Synthetase Activity ◽  
Acyltransferase Activity ◽  
Acyl Acceptor ◽  
Aspartic Acid Residue ◽  
Membrane Bound

ABSTRACT Sequence analysis of membrane-bound glycerolipid acyltransferases revealed that proteins from the bacterial, plant, and animal kingdoms share a highly conserved domain containing invariant histidine and aspartic acid residues separated by four less conserved residues in an HX4D configuration. We investigated the role of the invariant histidine residue in acyltransferase catalysis by site-directed mutagenesis of two representative members of this family, the sn-glycerol-3-phosphate acyltransferase (PlsB) and the bifunctional 2-acyl-glycerophosphoethanolamine acyltransferase/acyl-acyl carrier protein synthetase (Aas) ofEscherichia coli. Both the PlsB[H306A] and Aas[H36A] mutants lacked acyltransferase activity. However, the Aas[H36A] mutant retained significant acyl-acyl carrier protein synthetase activity, illustrating that the lack of acyltransferase activity was specifically associated with the H36A substitution. The invariant aspartic acid residue in the HX4D pattern was also important. The substitution of aspartic acid 311 with glutamic acid in PlsB resulted in an enzyme with significantly reduced catalytic activity. Substitution of an alanine at this position eliminated acyltransferase activity; however, the PlsB[D311A] mutant protein did not assemble into the membrane, indicating that aspartic acid 311 is also important for the proper folding and membrane insertion of the acyltransferases. These data are consistent with a mechanism for glycerolipid acyltransferase catalysis where the invariant histidine functions as a general base to deprotonate the hydroxyl moiety of the acyl acceptor.

scholarly journals Kinetic Studies on CphA Mutants Reveal the Role of the P158-P172 Loop in Activity versus Carbapenems

2016 ◽  
Vol 60 (5) ◽  
pp. 3123-3126 ◽  
Author(s):  
Carlo Bottoni ◽  
Mariagrazia Perilli ◽  
Francesca Marcoccia ◽  
Alessandra Piccirilli ◽  
Cristina Pellegrini ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Catalytic Efficiency ◽  
Kinetic Studies ◽  
Zinc Ion ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Wild Type ◽  
The Stability

ABSTRACTSite-directed mutagenesis of CphA indicated that prolines in the P158-P172 loop are essential for the stability and the catalytic activity of subclass B2 metallo-β-lactamases against carbapenems. The sequential substitution of proline led to a decrease of the catalytic efficiency of the variant compared to the wild-type (WT) enzyme but also to a higher affinity for the binding of the second zinc ion.

scholarly journals Probing the Role of Asp-120(81) of Metallo-β-lactamase (IMP-1) by Site-directed Mutagenesis, Kinetic Studies, and X-ray Crystallography

2005 ◽  
Vol 280 (21) ◽  
pp. 20824-20832 ◽  
Author(s):  
Yoshihiro Yamaguchi ◽  
Takahiro Kuroki ◽  
Hisami Yasuzawa ◽  
Toshihiro Higashi ◽  
Wanchun Jin ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals A tyrosine residue essential for catalytic activity in aminopeptidase A

1997 ◽  
Vol 327 (3) ◽  
pp. 883-889 ◽  
Author(s):  
Gilles VAZEUX ◽  
Xavier ITURRIOZ ◽  
Pierre CORVOL ◽  
Catherine LLORENS-CORTÈS
Keyword(s):  
Catalytic Activity ◽  
Transition State ◽  
Active Site ◽  
Consensus Sequence ◽  
Zinc Ion ◽  
Cysteine Residue ◽  
Enzymic Activity ◽  
Site Directed Mutagenesis ◽  
Tyrosine Residue ◽  
Aminopeptidase A

Aminopeptidase A (EC 3.4.11.7; APA) is a 130 kDa membrane-bound zinc enzyme that contains the consensus sequence HEXXH (residues 385-389) conserved among the zinc metalloprotease family. In this motif, both histidine residues and the glutamic residue were shown to be involved respectively in zinc co-ordination and catalytic activity. Treatment of APA with N-acetylimidazole results in a loss of enzymic activity; this is prevented by the competitive aminopeptidase inhibitor amastatin, suggesting the presence of an important tyrosine, lysine or cysteine residue at the active site of APA. A tyrosine residue was previously proposed to be involved in the enzymic activity of aminopeptidase N. Furthermore sequence alignment of mouse APA with other monozinc aminopeptidases indicates the presence of a conserved tyrosine (Tyr-471 in APA). The functional role of Tyr-471 in APA was investigated by replacing this residue with a phenylalanine (Phe-471) or a histidine (His-471) residue by site-directed mutagenesis. Kinetic studies showed that the Km values of both mutants were similar to that of the wild-type enzyme, whereas kcat values were decreased by three orders of magnitude and corresponded to a variation in free energy of the rate-limiting step by 4.0 and 4.2 kcal/mol (0.96 and 1.00 kJ/mol) for the Phe-471 and His-471 mutants respectively. The mutation did not modify the inhibitory potency of a thiol-containing inhibitor that strongly chelates the active-site zinc ion, whereas that of a putative analogue of the transition state presumed to mimic the reaction intermediate was reduced. Taken together, these results strongly suggest that the Tyr-471 hydroxy group participates in catalysis by stabilizing the transition state complex through interaction with the oxyanion.

scholarly journals Brain ACE2 activation following brain aminopeptidase A blockade by firibastat in salt-dependent hypertension

2021 ◽  
Vol 135 (6) ◽  
pp. 775-791
Author(s):  
Reda Hmazzou ◽  
Yannick Marc ◽  
Adrien Flahault ◽  
Romain Gerbier ◽  
Nadia De Mota ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Renin Angiotensin System ◽  
Vasopressin Release ◽  
Angiotensin System ◽  
Angiotensin Converting Enzyme 2 ◽  
Zinc Metalloprotease ◽  
Angiotensin Iii ◽  
Membrane Bound ◽  
Aminopeptidase A ◽  
The Brain

Abstract In the brain, aminopeptidase A (APA), a membrane-bound zinc metalloprotease, generates angiotensin III from angiotensin II. Brain angiotensin III exerts a tonic stimulatory effect on the control of blood pressure (BP) in hypertensive rats and increases vasopressin release. Blocking brain angiotensin III formation by the APA inhibitor prodrug RB150/firibastat normalizes arterial BP in hypertensive deoxycorticosterone acetate (DOCA)-salt rats without inducing angiotensin II accumulation. We therefore hypothesized that another metabolic pathway of brain angiotensin II, such as the conversion of angiotensin II into angiotensin 1-7 (Ang 1-7) by angiotensin-converting enzyme 2 (ACE2) might be activated following brain APA inhibition. We found that the intracerebroventricular (icv) administration of RB150/firibastat in conscious DOCA-salt rats both inhibited brain APA activity and induced an increase in brain ACE2 activity. Then, we showed that the decreases in BP and vasopressin release resulting from brain APA inhibition with RB150/firibastat were reduced if ACE2 was concomitantly inhibited by MLN4760, a potent ACE2 inhibitor, or if the Mas receptor (MasR) was blocked by A779, a MasR antagonist. Our findings suggest that in the brain, the increase in ACE2 activity resulting from APA inhibition by RB150/firibastat treatment, subsequently increasing Ang 1-7 and activating the MasR while blocking angiotensin III formation, contributes to the antihypertensive effect and the decrease in vasopressin release induced by RB150/firibastat. RB150/firibastat treatment constitutes an interesting therapeutic approach to improve BP control in hypertensive patients by inducing in the brain renin–angiotensin system, hyperactivity of the beneficial ACE2/Ang 1-7/MasR axis while decreasing that of the deleterious APA/Ang II/Ang III/ATI receptor axis.

Synthesis of Spinach Phosphoribulokinase and Ribulose 1,5-Bisphosphate in Escherichia coli

1992 ◽  
Vol 19 (3) ◽  
pp. 213 ◽  
Author(s):  
GS Hudson ◽  
MK Morell ◽  
YBC Arvidsson ◽  
TJ Andrews
Keyword(s):  
Escherichia Coli ◽  
Thiol Group ◽  
Site Directed Mutagenesis ◽  
Atp Binding Site ◽  
Carbon Reduction ◽  
Cell Extracts ◽  
Reduction Cycle ◽  
Fold Reduction ◽  
Carbon Reduction Cycle

Phosphoribulokinase catalyses the reaction which supplies the CO2-acceptor of the photosynthetic carbon reduction cycle, D-ribulose 1,5-bisphosphate (RuBP). In plants, this enzyme is inactivated in the dark by oxidation of two cysteinyl residues, Cys16 and Cys55, on the same subunit. A cDNA for spinach phosphoribulokinase was isolated by amplification from leaf RNA and cloned into a bacterial expression plasmid to give plasmid pMMPRK. Escherichia coli carrying pMMPRK grown in rich medium accumulated both the enzyme phosphoribulokinase and its reaction product RuBP. This accumulation of RuBP severely retarded growth of the cells on minimal media. The enzyme was isolated from cell extracts and shown to be kinetically similar to authentic phosphoribulokinase isolated from spinach leaves. Cys55 was altered by site-directed mutagenesis to explore the role of this residue in catalysis and regulation. Alteration of Cys55 to Ser or Gly caused a 10-fold reduction in Vmax and altered Km(ATP). These results are consistent with Cys55 being located at the ATP-binding site but the side chain of this residue is clearly not essential for catalysis. Loss of the Cys55 thiol group accounts for most, but not all, of the loss of activity which occurs during dark inactivation of phosphoribulokinase.

scholarly journals Structural insight into the catalytic mechanism and inhibitor binding of aminopeptidase A

2020 ◽  
Vol 477 (21) ◽  
pp. 4133-4148
Author(s):  
Pierre Couvineau ◽  
Hugo De Almeida ◽  
Vincent Leroux ◽  
Bernard Roques ◽  
Bernard Maigret ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Catalytic Mechanism ◽  
Site Directed Mutagenesis ◽  
Conserved Sequence ◽  
Angiotensin Iii ◽  
Membrane Bound ◽  
Aminopeptidase A ◽  
Dynamics Simulations ◽  
The Brain ◽  
S2 Subsite

Aminopeptidase A (APA) is a membrane-bound monozinc aminopeptidase. In the brain, APA generates angiotensin III which exerts a tonic stimulatory effect on the control of blood pressure (BP) in hypertensive animals. The oral administration of RB150 renamed firibastat by WHO, an APA inhibitor prodrug, targeting only the S1 subsite, decreases BP in hypertensive patients from various ethnic origins. To identify new families of potent and selective APA inhibitors, we explored the organization of the APA active site, especially the S2′ subsite. By molecular modeling, docking, molecular dynamics simulations and site-directed mutagenesis, we revealed that Arg368 and Arg386, in the S2′ subsite of human APA established various types of interactions in major part with the P2′ residue but also with the P1′ residue of APA inhibitors, required for their nanomolar inhibitory potency. We also demonstrated an important role for Arg368 in APA catalysis, in maintaining the structural integrity of the GAMEN motif, a conserved sequence involved in exopeptidase specificity and optimal positioning of the substrate in monozinc aminopeptidases. This arginine together with the GAMEN motif are key players for the catalytic mechanism of these enzymes.

A Mutational Analysis of dishevelled in Drosophila Defines Novel Domains in the Dishevelled Protein as Well as Novel Suppressing Alleles of axin

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 747-762
Author(s):  
Andrea Penton ◽  
Andreas Wodarz ◽  
Roel Nusse
Keyword(s):  
Planar Cell Polarity ◽  
Mutational Analysis ◽  
Consensus Sequence ◽  
Point Mutations ◽  
Site Directed Mutagenesis ◽  
Missense Mutations ◽  
Genetic Screens ◽  
Planar Polarity ◽  
Overexpression Phenotype

Abstract Drosophila dishevelled (dsh) functions in two pathways: it is necessary to transduce Wingless (Wg) signaling and it is required in planar cell polarity. To learn more about how Dsh can discriminate between these functions, we performed genetic screens to isolate additional dsh alleles and we examined the potential role of protein phosphorylation by site-directed mutagenesis. We identified two alleles with point mutations in the Dsh DEP domain that specifically disrupt planar polarity signaling. When positioned in the structure of the DEP domain, these mutations are located close to each other and to a previously identified planar polarity mutation. In addition to the requirement for the DEP domain, we found that a cluster of potential phosphorylation sites in a binding domain for the protein kinase PAR-1 is also essential for planar polarity signaling. To identify regions of dsh that are necessary for Wg signaling, we screened for mutations that modified a GMR-GAL4;UAS-dsh overexpression phenotype in the eye. We recovered many alleles of the transgene containing missense mutations, including mutations in the DIX domain and in the DEP domain, the latter group mapping separately from the planar polarity mutations. In addition, several transgenes had mutations within a domain containing a consensus sequence for an SH3-binding protein. We also recovered second-site-suppressing mutations in axin, mapping at a region that may specifically interact with overexpressed Dsh.

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