Amino Acid Metabolism

Amino Acid Metabolism
by:Hanley N. Abramson
Professor of Pharmaceutical Sciences
Wayne State University

December 2009

Dynamics of Protein And Amino Acid Metabolism
Dietary Proteins Digestion to Amino Acids
Digestion of Proteins
Stomach: Pepsinogen Pepsin (max. act. pH 2)
Small Intestine: Trypsinogen Trypsin
Trypsin cleaves:
Chymotrypsinogen to chymotrypsin
Proelastase to elastase
Procarboxypeptidase to carboxypeptidase
Aminopeptidases (from intestinal epithelia)

Enteropeptidase
Lumen
Amino Acids Oligopeptides
Intestinal Absorption
Oligopeptides
Amino Acids
Peptidases
Blood
Transport
Protein
Incorporation of NH4+ Into Organic Compounds
Carbamoyl
Phosphate
Synthase I
(CPS-I)
Glutamate
dehydrogenase
a-Ketoglutarate
Glutamate
TCA Cycle
mitochondria
Glutamine
Glutamate
Glutamine
Synthase
Mg++
N of glutamine donated to other compounds in synthesis of purines, pyrimidines, and other amino acids
Biosynthesis of Amino Acids: Transaminations
Glutamate a-Ketoglutarate
Oxaloacetate Aspartate
Glutamate-Pyruvate
Aminotransferase
(Alanine Transferase ALT)
Glutamate-Oxaloacetate
Aminotransferase
(Aspartate Transferase AST)
Blood levels of these aminotransferases, also called transaminases, are important indicators of liver disease
Metabolic Classification of the Amino Acids
* Essential and Non-essential
* Glucogenic and Ketogenic
Non-Essential Amino Acids in Humans
* Not required in diet
* Can be formed from a-keto acids by transamination and subsequent reactions
* Alanine
* Asparagine
* Aspartate
* Glutamate
* Glutamine
* Glycine
* Proline
* Serine
* Cysteine (from Met*)
* Tyrosine (from Phe*)
* Essential amino acids
Essential Amino Acids in Humans
* Required in diet
* Humans incapable of forming requisite carbon skeleton
* Arginine*
* Histidine*
* Isoleucine
* Leucine
* Valine
* Lysine
* Methionine
* Threonine
* Phenylalanine
* Tryptophan

* Essential in children, not in adults

Glucogenic Amino Acids
* Metabolized to a-ketoglutarate, pyruvate, oxaloacetate, fumarate, or succinyl CoA
Phosphoenolpyruvate Glucose
* Aspartate
* Asparagine
* Arginine
* Phenylalanine
* Tyrosine
* Isoleucine
* Methionine
* Valine
* Glutamine
* Glutamate
* Proline
* Histidine
* Alanine
* Serine
* Cysteine
* Glycine
* Threonine
* Tryptophan

Ketogenic Amino Acids
* Isoleucine
* Leucine *
* Lysine *
* Threonine
* Tryptophan
* Phenylalanine
* Tyrosine

Amino Acids Formed From a-Ketoglutarate
Transamination or
Glutamate
Urea Formation
Blood Urea Nitrogen
Synthesis of Nitric Oxide
Nitric oxide synthase (NOS)
Nitric Oxide
Conversion of Serine to Glycine
Sulfur-Containing Amino Acids
Homocysteine
Homocysteinuria
High blood levels of homocysteine associated with cardiovascular disease
Methionine Metabolism: Methyl Donation
Pneumocystis carinii infectons
Creatine and Creatinine
Normal Utilization of Phenylalanine ....

Amino Acid Metabolism.ppt