AA, Proteins, Enzymes (Biochem) Flashcards
AA that have R-groups with + charge at physiologic pH
- Arginine and Lysine (both are found in histones)
- histidine has a + charged R group at neutral pH, that is found at the active site of enzymes
AA that have R-groups with - charge at physiologic pH
aspartic acid and glutamic acid
AA that buffers well in proteins at physiologic pH
Histidine
Essential AA
P - phenylalanine (NOT PROLINE)
V - valine
T - threonine (NOT TYROSINE)
T - tryptophan (NOT TYROSINE)
I - isoleucine
M - methionine
H - histidine
A - arginine (only essential in kids*)
L - leucine
L - lysine
*kids have + N balance and need more N
Negative Nitrogen balance associated with
- protein malnutrition (kwashiorkor)*
- dietary deficiency of even one essential AA
- starvation
- uncontrolled diabetes
- infection
- Don’t confuse with marasmus = chronic deficiency of calories. These patients do not present with edema like patients with kwashiorkor
Positive Nitrogen balance associated with
- growth
- pregnancy
- recovery phase of injury/surgery
- recovery from condition associated with negative nitrogen balance
a child with PKU has how many essential AA?
- Normal adults only need 9 (arginine is only essential in kids)
- normal kids only need 10 (arginine)
- kids with PKU need 11 (also need tyrosine)
Do competitive or non-competitive inhibitor increase Km?
Competitive inhibitors increase Km
How do you change Vmax?
add more enzyme
noncompetitive inhibitors
- no effect on Km
- DECREASE Vmax
Km =
substrate concentration at which enzyme is at 1/2 Vmax
Competitive inhibitors
- increase Km
- no effect on Vmax
This enzyme is a major precursor in gluconeogenesis
Alanine (nonpolar)
AA with Nonpolar, aliphatic side chains
- glycine (gly)
- alaine (Ala)
- valine (Val)
- leucine (Leu)
- ieoleucine (Ile)
- proline (Pro) (has secondary amine)
6 AA with Nonpolar, aliphatic side chains - VP GAILe
- A is not Arginine
- L is isoleucine, not lysine
Hartnup’s Disease
- AR
- affects absorption of non polar AA
- tryptophan not absorbed therefore can’t make serotonin, melatonin, niacin
- symptoms: photosensitivity, nystagmus, tremor, ataxia (neurological)
- Tx: high protein diet
AA with aromatic side chains
3 total:
- phenylalanine (Phe)
- tyrosine (Tyr)
- tryptophan (Trp)
- tryptophan used to make serotonin, melatonin, niacin
- tyrosine is used to make T3, T4, and melanin
AA used to make catecholamines T3, T4 and precursor to melanin
Tyrosine
AA with polar, uncharged R groups
- serine (Ser)
- threonine (Thr)*
- cysteine (Cys)
- asparagine (Asn)
- glutamine (Gln)
- methionine (Met can be considered nonpolar or polar bc has S)
- Threonine target of O-glycosylation in Golgi
- STAG MC
- A = asparagine
- T = threonine
which AA is the precursor to NO
- Arginine
- Remember: Essential AA in kids
Body uses which AA to carry NH3 in blood
Glutamine
AA that contain Sulfur
- Cysteine and Methionine
- targets of N-glycosylation that begins in ER
protein breakdown occurs in 2 locations
- lysosomal proteases digest endocytosed proteins
- large cytoplasmic complexes (proteasomes) digest older or abnormal proteins that have been covalently tagged with ubiquitin for destruction
Which AA are precursors for catecholamines
phenylalanine and threonine
catecholamine ex: Norepinephrine, Epinephrine, Dopamine
Hydrophilic AA
- Positively charged AA (3), Negatively charged AA (2), Polar uncharged AA (6)
- 11 total: aspartate, glutamate, lysine, arginine, histidine, serine, threonine, cysteine, methionine, asparagine, glutamine
Which are branched-chain AA whose metabolism is abnormal in maple syrup urine disease?
valine, leucine and isoleucine (all nonpolar)
which AA is a secondary amine whose presence in a protein disrupts normal secondary structure?
proline
hydrophobic AA
9 total: glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan
Which AA can form serotonin and niacin
Tryptophan
- Is Hartnup’s disease AD or AR?
- symptoms? what causes them?
- AR
- tryptophan not absorbed therefore can’t make serotonin, melatonin, niacin
- symptoms: photosensitivity, nystagmus, tremor, ataxia (neurological)
Tyrosine is used to make ??
catecholamines T3, T4 and is a precursor to melanin
kids with PKU also need what AA?
tyrosine (+ 10 essential AA for a total of 11)
