Angiotensin I-Converting Enzyme (ACE):

From Bench To Clinic

Angiotensin I-Converting Enzyme (ACE):

From Bench To Clinic

ByByDr. Amr S. MoustafaAss. Prof. and Consultant

Medical Biochemistry Dept.

Dr. Amr S. MoustafaAss. Prof. and Consultant

Medical Biochemistry Dept.

OutlinesOutlinesACE ProteinACE GeneACE PolymorphismACE and DiseasesSummary and ConclusionsACE Inhibitors

OutlinesOutlinesACE ProteinACE GeneACE PolymorphismACE and Diseases

Summary and ConclusionsACE Inhibitors

ACE ProteinACE ProteinStructure: Zinc-Metallopeptidase (EC 3.4.15.1)

Physiological Functions

Substrates: Natural and SyntheticDistribution

ACE Isoforms

ACE Isoforms

*Somatic Testicular

Gene 17q23 17q23

Distribution Endothelial and

Epithelial

Sperm

Mr in kDa 146 (160) 80 (90)

Active site(s) 2 plus 2 Zn 1 plus 1 Zn

*ACE2 : Regulator of cardiac function

Structure of sACE and gACE

Structure of sACE and gACE

The 3-D Structure of gACE

The 3-D Structure of gACE

ACE ProteinACE ProteinStructure: Zinc-Metallopeptidase

Physiological Functions

Substrates: Natural and Synthetic

Distribution

ACE SubstratesACE Substrates

Natural: Angiotensin I Bradykinin Others, neuropeptides, hematopoietic, …

Synthetic: Hippuryl-glycyl-glycine Hippuryl-histidyl-leucine (HHL) Furylacryloyl-phenylalanyl-glycyl-glycine (FAPGG)

ACE DistributionACE Distribution

Cellular Origin: Vascular Endothelium Others: Epithelial, Neuronal, …

Tissue Distribution: Lungs, Brain, kidneys, adrenals Male Reproductive tract

Plasma ACE

Physiological Functions

Physiological Functions

Vascular toneCardiac Functions

Neuronal Metabolism

Reproduction

Hematopoiesis

Renin-Angiotensin System

Renin-Angiotensin System

Measurement of ACE

Measurement of ACE

ACE Activity: Spectrophotometric, Flurometric, Radiometric, Chromatographic

Synthetic substrates

ACE Level: ELISA and Radioimmunoassay

Specific anti-human ACE antibody

Plasma ACE Level

Plasma ACE Level

ACEGranulomatous:

Sarcoidosis, SilicosisGaucher, Leprosy

Non-granulomatous:Hyperthyroidism, Cholestasis

ACEVascular endothelial damage

DVTChemo-toxicity in cancer treatment

Plasma ACE LevelPlasma ACE Level

Large inter-individual variation:

Ref. range 37-202 ng/ml ~ Six fold

Sex, Age, Hormonal, Environmental, . .

Gene Effect:

Similar intra-familial ACE levels

And/or

ACE GeneACE Gene

Structure

Polymorphism

Genotype/phenotype

Polymorphism and diseases

Structure of ACE GeneStructure of ACE Gene

3’ 5’

E1 E13 E14 E26

DNA

E1 E12 E14 E26

5’ 3’mRNA

E13E14 E26

5’ 3’mRNA

sACE

gACE

ACE

ACE Gene Insertion/Deletion (I/D)

Polymorphism

ACE Gene Insertion/Deletion (I/D)

Polymorphism

Two alleles: I and DThree Genotypes: II, ID, and DD

I or D of 287 bp in intron 16

Clinical Significance: Linkage to diseases: Controversial Intron location: No direct effect on ACE expression

PCR for ACE genotypesPCR for ACE genotypes

1 2 3 4

490 bp

190 bp

II ID DD

The Relationship Between

Genotype/Phenotype of ACE

The Relationship Between

Genotype/Phenotype of ACE

GenotypeII

(N = 14)

ID

(N = 37)

DD

(N = 29)

Distribution 18% 46% 36%

Phenotype

ACE ng/ml299+49 393+67 494+88

Allele Frequency: I = 0.4 and D = 0.6

Genotype/Phenotype of ACE

Caucasian Vs Asian

Genotype/Phenotype of ACE

Caucasian Vs Asian

Caucasian Asian

DD Genotype 36% 14%

ACE level60% higher DD than II

No differenceDD and II

Best response to ACEi

DD II

ACE I/D Polymorphism and Diseases: Heart

Diseases

ACE I/D Polymorphism and Diseases: Heart

Diseases

DD and ID are independent risk factors for CAD in Turkish

DD and ID are associated with CHD

DD is associated with heart failure progression and worsens its outcome

ACE I/D Polymorphism and Diseases: T2DM

ACE I/D Polymorphism and Diseases: T2DM

DD is associated with T2DM and its renal and vascular complications in Caucasian

DD is a risk factor DM and Nephropathy in Japanese

DD is a risk factor for renal Complications in Chinese

ACE I/D Polymorphism and Diseases: Nephropathy

ACE I/D Polymorphism and Diseases: Nephropathy

DD showed higher frequency in non-SS INS in Taiwan

II is more frequent in SS-nephrotic Syndrome in India

No difference in genotype frequencyin NS in Indonesia

No difference in genotype frequencyin DM with ESRD in Taiwan

ACE InhibitorsACE Inhibitors

The first was Captopril, 1981

Design and mechanism: The active site for carboxpeptidase A Tight-binding to the active site Thiol or other groups coordinate Zn

Mixed-type inhibition: Plasma and membrane-bound ACE

Little discrimination for the 2 active sites

ACE Inhibitors: Clinical Uses

ACE Inhibitors: Clinical Uses

First-line therapy: Hypertension Congestive heart failure Myocardial infarction

Other common indications: Nephropathy Renal transplant patients

ACE Inhibitors: Limitations

ACE Inhibitors: Limitations

Varied response among different persons

? Modulating effect of ACE I/D polymorphism Better response in DD Vs II Caucasian

Pharmacogenetic Tests: Would screening for I/D polymorphism before prescription of ACE inhibitors be cost-effective? (Pharmacoeconomic)

ACE Inhibitors: Future

ACE Inhibitors: Future

New generation of ACE inhibitors: Recent crystal-structure Less side effects More clinical effectiveness

Active-site specific inhibitors: N- or C-

ACE2-specific inhibitors

Tailor-made Therapy

Conclusions-1Conclusions-1Molecular cloning and crystal-structureof ACE: Rapid advance and More focus on ACE research

ACE I/D polymorphism and diseases:

Debate and Paradox Better research design Careful reporting of genetic data

Conclusions-2Conclusions-2

Genetic-based therapy is not yet a common clinical practice; but, genetic targeting will become the standard medical care soon

Development of new generation of ACE inhibitors is warranted

Conclusions-3Conclusions-3$Sutton’s Low of Clinical Research:

The research energies should be directed where the clinical impact is likely highest; i.e., “to go where the money is”

$Willie Sutton (1950):

A famous Chicago bank robber

AcknowledgmentAcknowledgment

Prof. Bruno Baudin, Saint-Antoine Hospital Paris, France and

Universite de Basse Normandie, France