Amino Acids

1
Amino Acids

• Structure
• ? - amino carboxylic acid
• Carboxyl carbon 1 (C O O-)
• ? carbon
• Amino group NH3
• Peptide bonds formed between amino acids at ?
  amine of one a.a. and carboxyl group of another

2
Amino Acid Metabolism

• A.A. undergo constant oxidative degradation
  during
• Normal synthesis and degradation of proteins
• When we ingest more a.a. than our bodies can use
  to make proteins or convert to other substances
• During starvation, fasting, dieting uncontrolled
  diabetes mellitus, when carbohydrates are not
  available

3
Amino Acid Degradation

• Major site of degradation is in liver
• Catabolism of individual a.a. Involves two major
  stages
• Amino acids lose their nitrogen atoms by either
  oxidative deamination or transamination ?convert
  to glutamate
• Resulting carbon skeletons are fed into specific
  energy-yielding pathways to retrieve their
  chemical energy
• Muscle removes most amino groups for
  branched-chain amino acids

4
Oxidative Deamination

• Process occurs in mitochondrial matrix of
  liver NAD--?NADH
• Amino acid ??Glutamate??NH4 Glutamate
  dehydrogenase
• ?-ketoglutarate (Krebs cycle intermediate)

5
Amino Acid Metabolism

• Transamination most common route for A.A.
  nitrogen including muscle tissue
• Transfer of amine group
• Glutamate is involved
• Glutamate pyruvate ?? alanine ? -
  ketoglutarate reaction favors to the right in
  muscle and left in liver

6
Glucose-Alanine Cycle

• Leucine, isoleucine, valine (available in muscle)
• NH2- split from leucine combines w/pyruvate to
  form alanine
• Alanine enters circulation picked up in liver
  where it is deaminated to form urea and pyruvate
• Pyruvate is converted to liver glycogen or
  glucose
• Glucose can be re-circulated to working muscle
• When most amino groups are removed, citric acid
  intermediates such as oxaloacetate, fumarate are
  formed

7
Amino Acid Oxidation

• Proteins---gtamino acids---gtDeamination---gt Carbon
  skeleton---gt CHO or FA Metabolism
• During prolonged exercise, when muscle glycogen
  and blood glucose concentrations are low, the
  incorporation of the carbon skeletons from AA
• Main AA oxidized in skeletal muscle are branched
  chain AA isoleucine, leucine, valine, glutamine
  and glutamate

8
Replenishment of Energy Stores

• First What is depleted (energetically)?
• Phosphagens (ATP PC)
• Glycogen stored in muscle liver
• What about lipids? Are they depleted?
• Not replenished during recovery are replenished
  indirectly through replenishment of carbohydrate

9
Oxygen Debt vs. Recovery Oxygen

• Oxygen Debt (AV Hill) stated most lactic acid
  formed during exercise was converted to glycogen
  (80),
• Margaria introduced concept of Alactacid and
  lactacid debt components
• Contemporary termed Recovery Oxygen or Excess
  post-exercise oxygen consumption (EPOC)
• Fast component and slow component

10
Fast Component

• Phosphagens (ATP PC)
• Elevated oxygen consumption during this time
  period fuels the bodys need for
• restoring myoglobin w/oxygen
• restoring blood levels of O2
• O2 cost of breathing
• Increased heart rate (myocardial O2
• Replenish phosphagens
• Magnitude of Fast Component volume is related to
  previous exercise intensity

11
Fast Component Recovery

• Rapid recovery of phosphagens at start of
  recovery later slows down
• 70 - 30 seconds
• 100 - 3-5 minutes
• PC recovery
• 84 restored in 2 minutes
• 89 restored in 4 minutes

12
Replenishment of Energy Stores

• Restoration of ATP PC
• Half-time 30 sec 1 min 3/4s 1.5 min 7/8
  3 min 63/64
• Muscle glycogen
• .7 g/kg body wt/hr, carbohydrates with high
  glycemic index -
• On average 5 of muscle glycogen used during
  exercise is re-synthesized each hour after
  exercise minimal 20 hrs to restore muscle
• Lactic acid removal-oxidation

13
O2 - Myoglobin Stores

• Found in skeletal muscle
• Store for oxygen
• Involved functionally in transfer of oxgyen
• Inside the cell to inside the mito
• 11.2 ml/kg of muscle or 500 ml
• Functional significance related to intermittent
  exercise - rapidly restored following short bout
  of exercise

14
Exercise Related factors that cause extra O2
consumption

• Temperature effects mitochondrial O2
  consumption, leading to decline in energy
  trapping efficiency (Brooks, 2000)
• BMR? 13 per degree Celsius increase in body temp
• Sympathetic stimulation increases metabolic
  rate of numerous tissues