protein metabolism l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Protein Metabolism PowerPoint Presentation
Download Presentation
Protein Metabolism

Loading in 2 Seconds...

play fullscreen
1 / 22

Protein Metabolism - PowerPoint PPT Presentation


  • 189 Views
  • Uploaded on

Protein Metabolism. Catabolism. Synthesis. Amino acids. Protein. Gut. Degradation. Deposition. Protein turnover. Protein synthesis. On-going, semicontinuous activity in all cells but rate varies greatly between tissues. Rate of protein synthesis. Protein synthesis.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Protein Metabolism' - MikeCarlo


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
protein turnover

Catabolism

Synthesis

Amino

acids

Protein

Gut

Degradation

Deposition

Protein turnover
protein synthesis
Protein synthesis
  • On-going, semicontinuous activity in all cells but rate varies greatly between tissues
protein synthesis5
Protein synthesis
  • On-going, semicontinuous activity in all cells but rate varies greatly between tissues
  • Rate is regulated by hormones and supply of amino acids and energy
  • Energetically expensive
    • requires about 5 ATP per one peptide bond
  • Accounts for about 20% of whole-body energy expenditure
protein degradation
Protein degradation
  • Also controlled by hormones and energy status
  • Method to assist in metabolic control
    • turns off enzymes
protein synthesis and degradation
Protein synthesis and degradation
  • Synthesis must exceed degradation for net protein deposition or secretion
  • Changes in deposition can be achieved by different combinations of changes in synthesis and degradation
protein turnover9

Catabolism

Synthesis

Amino

acids

Protein

Gut

Degradation

Deposition

Protein turnover
protein synthesis and degradation10
Protein synthesis and degradation
  • Synthesis must exceed degradation for net protein deposition or secretion
  • Changes in deposition can be achieved by different combinations of changes in synthesis and degradation
  • Allows for fine control of protein deposition
protein synthesis and degradation11
Protein synthesis and degradation
  • Other possible reasons for evolution of protein turnover include
    • Allows post-translational conversion of inactive peptides to active forms (e.g., pepsinogen to pepsin)
    • Minimizes possible negative consequences of translation errors
protein catabolism
Protein catabolism
  • Some net catabolism of body proteins occurs at all times
    • Expressed as urinary nitrogen excretion
      • yields urea
  • Minimal nitrogen excretion is termed endogenous urinary nitrogen (EUN)
urinary nitrogen excretion
Urinary nitrogen excretion

LIVER

Amino acids

keto acids

NH3

CO2

Urea

Blood

KIDNEY

Urea

Urine

protein catabolism14
Protein catabolism
  • Occurs when
    • dietary protein exceeds requirements
    • composition of absorbed amino acids is unbalanced
    • gluconeogenesis is increased
amino acid metabolism
Amino acid metabolism
  • Biosynthesis of nonessential amino acids
  • Catabolism
  • Conversion to glucose or fat
  • Urea cycle
biosynthesis of nonessential amino acids
Biosynthesis of nonessential amino acids
  • Transamination reactions
    • allow extensive interconversion between nonessential amino acids
    • requires vitamin B6 as a coenzyme
biosynthesis of nonessential amino acids17
Biosynthesis of nonessential amino acids
  • Tyrosine
    • From phenylalanine (PKU; 1 in 15,000)
      • hydroxylation of phenylalanine
      • important in adrenaline, noradrenaline, thyroxine and melanin synthesis
biosynthesis of nonessential amino acids18
Biosynthesis of nonessential amino acids
  • From intermediates of glycolysis
    • from 3-phosphoglycerate and glycine
      • serine
        • phosphatidylserine
    • from serine
      • glycine
        • high demand (10-50x greater than dietary intake)
        • synthesis of purines, collagen, bile salts and glutathione
      • cysteine
        • S from methionine
        • glutathione
biosynthesis of nonessential amino acids19
Biosynthesis of nonessential amino acids
  • From intermediates of TCA
    • From oxaloacetate
      • aspartate
        • amino donor in urea synthesis
        • pyrimidine and purine synthesis
      • asparagine
biosynthesis of nonessential amino acids20
Biosynthesis of nonessential amino acids
  • From intermediates of TCA
    • From α-ketoglutarate
      • glutamate/glutamine
        • purine and pyrimidine synthesis
      • proline
      • arginine
        • intermediate in the urea cycle
        • source of vasodilator, nitric oxide
catabolism
Catabolism
  • Oxidative deamination
    • Released NH3 converted to urea
    • Carbon skeleton can be
      • oxidized (TCA cycle)
      • used for glucose synthesis (gluconeogenesis)
      • used for fat synthesis
ketogenic amino acids
Ketogenic amino acids
  • Leucine and isoleucine
    • converted to acetoacetate or acetyl CoA in liver
      • fuel for other tissues