BMB 401 Lecture 31 Flashcards

Proteolysis of Dietary Protein Begins in______
Pepsinogen:_______
Pepsin:_______

Stomach
Zymogen
Active Enzyme-activated by low pH
-low pH also makes protein accessible to protease

Pancreatic Proteases
Oligo-peptides: proteolyzed:______ on luminal surface
Di- and Tri-peptides cleaved by ___ in enterocytes.
Amino acids are: _______


aminopeptidases

peptidases

used in synthetic reactions, or catabolized

Zymogen.........................Active Enzyme??
Pepsinogen-Stomach
Chymotrypsinogen-Pancreas
Trypsinogen-Pancreas
Procarboxypeptidase-Pancreas
Proelastase-Pancreas

Pepsinogen-Pepsin
Chymotrypsin-Chymotrypsin
Trypsinogen-Trypsin
Procarboxypeptidase-Carboxypeptidase
Proelastase-Elastase

Ubiquitin binds to proteins through formation of an ______ bond with _____residues

isopeptide,Lysine

19S
20s

19S
ATPase
Isopeptidase
20s conformational change

AMINO ACID CATABOLISM
WHERE?
STRATEGY?

Where:

Liver :
Major site of amino acid catabolism

Muscles: Branched chain amino acids
Basic Strategy:
Remove amino group: NH4+
Utilize the carbon skeletons: Synthesis or energy


7 Carbon Skeleton Metabolites


Pyruvate

Acetyl CoA

Acetoacetyl CoA
? -Ketoglutarate

Succinyl Co A

Fumarate

Oxaloacetate


Two important transminases:

Aspartate transaminase (AST)

-High levels in blood are sign of inflammation, liver disease

Alanine transaminase (ALT)

Aspartate + ?-KG ? OAA + Glutamate
Malate Aspartate Shuttle
Alanine + ?-KG ? Pyruvate + Glutamate
Alanine Cycle

Alanine Cycle-muscles

Can use branched chain AA for fuel
Do not have urea cycle to process ammonium
Amino group sent to liver as part of alanine (also glutamine)

Oxidative Deamination

Oxidation to form an aldimine Shiff-base,
Hydrolysis to yield free ammonium ion and ?-ketoglutarate.

Urea Cycle


In the Mitochondrial Matrix

a) Activation of Bicarbonate with ATP, to form
Carboxyphosphate b) Condensation of Carboxyphosphate with
Ammonia c) Activation of carbamic acid with ATP to form
Carbamoyl Phosphate

4 fates of OAA

1.Transamination to make Aspartate
2.Condensation with Acetyl CoA to make Citrate > energy
3.Gluconeogenesis > energy export
4.Conversion to pyruvate then to acetyl Co A for FA synthesis

Which AA are....
Ketogenic?
Ketogenic & glucogenic?
Glucogenic?

Ketogenic- Lysine & Leucine
Both- Phe, Ile, Trp, Tyr (Phil Is Tripping on Tires)
Glycogenic-Other 14

Phenylalanine and Tyrosine Catabolism:

Hydroxylation of phenylalanine to tyrosine phenylalanine
hydroxylase
(this is an important enzyme to remember)
Deamination to form hydrophenylpyruvate
Formation of homogentisate
Next step requires homogentisate dioxygenase
(this is an important enzyme to remember)

Final products are Fumarate and Acetoacetate

Catabolism of Phenylalanine
Conversion to tyrosine by ______
Requires electron carrier______
Unlike FAD and NAD+ not vitamin derived


phenylalanine hydroxylase

tetrahydrobiopterin

Phenylketonuria (PKU)

Mutation in phenylalanine hydroxylas or insufficient amount tetrahydrobiopterin
Treatment: low he, high try

Alkaptonuria

Absence of the enzyme homogentisate oxigenase
Homogentisate is excreted in the urine and produces melanin-like
dark pigment when oxidized by air. This makes the urine
black. Relatively benign disease as homogentisate can be excreted.

Catabolism of Branched Chain Amino Acids:


Transamination -
Branched-chain amino acid transaminase
?-ketoglutarate is amine acceptor
yields glutamate and three different ?-ketoacids

Oxidative decarboxylation of ?-ketoacids -
Branched-chain ?-keto acid dehydrogenase complex
yields three different CoA derivatives.

Complex is similar to PDC
and ?KDH

Maple-syrup Urine Disease


Branched-chain ?-keto acid dehydrogenase
complex is missing or defective.
Oxidative decarboxylation of ?-ketoacids from branched-chain AA,
(Ile Val Leu) does not occur.