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MindMap Gallery Protein digestion and amino acid metabolism
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Protein digestion and amino acid metabolism
This is a mind map about protein digestion and amino acid metabolism. Undigested protein and unabsorbed digestion products are decomposed by Escherichia coli in the lower part of the large intestine. This decomposition is called putrefaction.
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Protein digestion and amino acid metabolism
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- Outline
Protein digestion and amino acid metabolism
General metabolic processes of amino acids
Breakdown of protein into amino acids in the body
Proteins degrade at different rates
half life
The t1/2 of protein in the liver is 1 to 8 days
Plasma protein t1/2 is about 10 days
The key enzymes t1/2 are both very short
ATP independent pathway
lysosome
Degrade foreign proteins, membrane proteins and intracellular long-lived proteins
ATP dependent pathway
Proteasome (ubiquitin)
Degrade abnormal proteins and short-lived proteins
Multiple ubiquitination to form ubiquitin chains
Amino acid metabolism library
exogenous protein
Absorbed amino acids from food protein
endogenous protein
Amino acids produced by the degradation of tissue proteins in the body and non-essential amino acids synthesized in the body
Amino acid catabolism begins with deamination
Oxidative catabolism of amino acids
transamination of amino acids
Aminotransferase (transaminase)
transferred to alpha-keto acid
Except lysine, threonine, proline and hydroxyproline
Liver and myocardium are most abundant
ALT activity is highest in the liver and AST activity is highest in the myocardium
Typical example
The prosthetic group of aminotransferase is vitamin B6 (pyridoxal phosphate)
alanine transferase
aspartate transferase
Oxidative deamination of amino acids
L-Glutamic acid (high rate)
L-glutamate dehydrogenase (non-aerobic) catalyzes oxidative deamination
Formation of α-ketoglutarate and ammonia
Allosteric inhibition of ATP and GTP, allosteric activation of ADP and GDP
Coenzyme NAD or NADP
combined deamination
Flavoenzymes in liver and kidney
prosthetic group FMN or FAD
Amino acids are oxidized to α-imino acids and hydrolyzed into corresponding α-keto acids to release ammonium ions.
Direct oxidation of molecular oxygen to form H2O2
Cleaved into oxygen and H2O by catalase
Conversion and decomposition of amino acid carbon chain skeleton
Complete oxidation via the tricarboxylic acid cycle
Amination to produce nutritionally essential amino acids
Oxaloacetate → Aspartic acid
Pyruvate → alanine
α-ketoglutarate→glutamic acid
Convert to sugar or lipid
Glucogenic amino acids, ketogenic amino acids, glucogenic and ketogenic amino acids
Metabolism of individual amino acids
decarboxylation
Coenzyme: pyridoxine phosphate
Histidine
Histamine is a vasodilator
Glutamic acid
GABA is an inhibitory neurotransmitter
Tryptophan
5-hydroxytryptamine is an inhibitory neurotransmitter and can constrict blood vessels.
Ornithine produces putrescine, which is then converted into arginine and arginine
Polyamine regulates cell growth
one carbon unit
concept
When amino acids are metabolized, a group containing only one carbon atom is produced.
carrier
Tetrahydrofolate
Amino acids produce one-carbon units that are interconvertible
primary source
Serine, glycine, histidine and tryptophan
Function
Participate in the synthesis of purines and pyrimidines
N10-CHO-F4H provides methyl group for purine synthesis
Sulfur-containing amino acids
methionine cycle
process
way out
Creatine, carnitine, choline, epinephrine
Methyl indirect donor
N5-CH3-FH4
methanesulfate synthase
Coenzyme: Vitamin B12
Creatine vs. Creatine Phosphate
S-adenosylmethionine provides methyl synthesis
Mainly synthesized in the liver, contained in cardiac muscle, skeletal muscle and brain tissue
M subunit (muscle type) B subunit (brain type)
MM is mainly in skeletal muscle, MB is mainly in cardiac muscle, and BB is mainly in brain
Cysteine
interconversion with cystine
converted to taurine
components of bile
Generate active sulfate radicals
PAPS
Aromatic amino acid metabolism
Phenylalanine and tyrosine metabolism
Carboxylation of phenylalanine to tyrosine
Produce phenylpyruvic acid in small amounts
tyrosine conversion
converted to catecholamines
Produce dopamine (neurotransmitter)
Dopamine produces norepinephrine and epinephrine
Key enzyme: tyrosine hydroxylase
regulated by product feedback
convert to melanin
generate dopa
Converts to indolequinone and polymerizes into melanin
tyrosinase
Complete metabolism
Intermediate product: homogentisic acid
Form fumaric acid and acetoacetic acid
Tryptophan catabolism
In the liver, catalyzed by tryptophan oxygenase
Decompose to give pyruvic acid and acetoacetate CoA
Ammonia metabolism
Enters the blood and forms blood ammonia
Brain tissue is sensitive to ammonia
source
Gut bacteria produce ammonia
Colon absorbs into blood
amino acid deamination
primary source
glutaminolysis
Renal tubular lumen discharge
transport
alanine-glucose cycle
glutamine transporter
brain and skeletal muscles
Glutamine synthase catalyzes the synthesis of glutamine, and glutaminase catalyzes its hydrolysis into glutamic acid and ammonia.
Consume ATP
Glutamine provides the amino group to convert aspartic acid into asparagine
way out
urea cycle
process
key enzyme
Carbamoyl phosphate synthase I initiation
Argininosuccinate synthase after activation
mid product
Ornithine, Citrulline, Arginine
adjust
high protein
key enzyme regulation
AGA activates CPS-I
Argininosuccinic acid synthesis
disorders of urea production
Hepatic encephalopathy, hyperammonemia
Nutritional effects and digestion and absorption of protein
nitrogen balance
total nitrogen balance
normal person
Nitrogen metabolism
Children, pregnant women and patients recovering from serious illness
negative nitrogen metabolism
Burn patients, patients with wasting diseases
nutritional value
nutritional essential amino acids
A brings a bright book
nutritional value of protein
complementary effect
Types and proportions
Digestion and absorption
Hydrolyzed in the stomach into peptides and a small amount of amino acids
Pepsinogen is activated by hydrochloric acid
Pepsinogen is activated by itself (autocatalysis)
coagulation
casein
digestion in small intestine
Endopeptidase
certain specificity
trypsin
Basic amino acid residue peptide bond
chymotrypsin
Aromatic amino acid residue peptide bond
elastase
Aliphatic amino acid residue peptide bond
exopeptidase
Carboxypeptidase (main)
Carboxypeptidase A
Terminal peptide bonds of various amino acid residues except proline, arginine, and lysine
Carboxypeptidase B
Terminal peptide bond composed of basic amino acid residues
Aminopeptidase
Pancreatic islet cells secrete trypsinogen
Duodenal secretion of enterokinase activates
Trypsin activation chymotrypsinogen, elastasegen and carboxypeptidase
Presence of trypsin inhibitors in pancreatic juice
1/3 amino acids and 2/3 oligopeptides
Absorption by active transport mechanism of small intestinal mucosal cells
7 carrier proteins
Exists in both renal tubules and muscle cells
Corruption
concept
Undigested proteins and unabsorbed digestion products are decomposed by Escherichia coli in the lower part of the large intestine. This decomposition is called putrefaction.
product
bacterial amino acid decarboxylase
Histidine, lysine, tryptophan, tyrosine and phenylalanine
Generates histamine, cadaverine, tryptamine, tyramine, and phenylethylamine
pseudoneurotransmitter
Bacterial deamination and blood urea infiltration
Liver produces urea
Other harmful products
Phenol, indole, methylindole and hydrogen sulfate
excreted in feces