AMINO ACIDS METABOLISM

Digestion and Absorption of Proteins

PROTEIN TURNOVER OCCURSIN ALL FORMS OF LIFE

Each day humans turn over 1–2% of their total body protein, principally muscle protein

Of the liberated amino acids, approximately 75% are reutilized

Excess amino acids are rapidly degraded

Ubiquitin Tags Proteins for Destruction

ANIMALS CONVERT α-AMINO NITROGEN TO VARIED END PRODUCTS

Ammonotelic : excrete ammonia (teleostean fish)

Uricotelic : excrete uric acid (birds)

Ureotelic : excrete urea (land animals including human)

BIOSYNTHESIS OF UREA

1

2

4

3 AMMONIA TRANSPORT

TRASAMINATION

except lysine, threonine, proline, and hydroxyproline

Alanine-pyruvate aminotransferase (alanine aminotransferase)

glutamate-α-ketoglutarate aminotransferase (glutamate aminotransferase)

TRANSAMINASI

OXIDATIVE DEAMINATION

L-glutamate dehydrogenase

OXIDATIVE DEAMINATION

Glutamine Synthase Fixes Ammoniaas Glutamine

NH3 metabolism in the liver

UREA CYCLE

Metabolic Integration of Nitrogen Metabolism

UREA CYCLE(LIVER)

MITOCHONDRIA

CYTOSOL

Ammonia Intoxication Is Life-Threatening

Symptoms of ammonia intoxicationinclude tremor, slurred speech, blurred vision, coma, and ultimately death.

METABOLIC DISORDERS ARE ASSOCIATED WITH EACH REACTION OF THE UREA CYCLE

All defects in urea synthesis result in ammonia intoxication

Clinical symptoms of urea cycle disorders : include vomiting, intermittent ataxia, irritability, lethargy, and mental retardation

Hyperammonemia Type 1. Carbamoyl phosphate synthase I deficiency

Hyperammonemia Type 2. A deficiency of ornithine transcarbamoylase

Citrullinemia. In this rare disorder, plasma and cerebrospinal fluid citrulline levels are elevated and 1–2 g of citrulline are excreted daily.

Argininosuccinicaciduria. Absence of argininosuccinase

Hyperargininemia. Low erythrocyte levels of arginase

Catabolism of the Carbon Skeletons of Amino Acids

Fates of the Carbon Skeletons of Amino Acids

Amino acid biosynthesis: overview

NUTRITIONALLY NONESSENTIAL AMINO ACIDS HAVE SHORT BIOSYNTHETIC PATHWAYS

Inborn errors of amino acid metabolism

DNA Replication

TRANSCRIPT

Structure of Eukaryotic Ribosomes

General Structure of tRNA Molecules

The genetic code (codon assignments in mammalian messenger RNA)

Features of the genetic code

Formation of aminoacyl-tRNA.

Recognition of the codon by the anticodon

ATP

ATP + Pi

BINDING OFAMINOACYL-TRNATO THE A SITE

PEPTIDE BONDFORMATION

(peptidyltransferase) TRANSLOCATION

Mechanism of Protein Synthesis

Termination Process of Protein Synthesis

regulation on gene expression.

The mechanism of repression and derepression of the lac operon

Antibiotic inhibitors of protein synthesis