Amino Acids Clinical Chemistry

what makes up an amino acid?

carboxyl group

amine group

R-group (differentiates)

what amino acids are ketogenic? (converted into Acetyl CoA => ketones)

leucine 

lysine

what amino acids are both glucogenic AND ketogenic?

phenylalanine

isoleucine

tyrosine

tryptophan

what amino acids are glucogenic? (can be converted into glucose)

alanine, glycine, threonine, cysteine, serine, arginine, proline, histidine, glutamine, glutamate, valine, methionine, threonine, asparagine, aspartate

what is a non-essential amino acid

amino acids the body can build itself

what is an essential amino acid

amino acids the body CANNOT build itself - must be obtained through dietary intake

what are the 10 essential amino acids

1. phenylalanine

2. valine

3. threonine

4. tryptophan

5. isoleucine

6. methionine

7. histidine

8. arginine

9. leucine

10. lysine

what is a neutrally charged amino acid called?

zwitterion/ampholyte

when an amino acid is placed in an alkaline solution, does it become an anion, a cation, or a zwitterion?

anion due to de-protonation of carboxyl and amine groups

when an amino acid is placed in an acidic solution, does it become an anion, a cation, or a zwitterion?

cation due to both carboxyl and amine groups being protonated 

An amino has a pI of 4.8.  What buffer pH would you need for this protein to occur as a zwitterion with no net charge?

pH of 4.8

An amino has a pI of 5.4.  What buffer pH would you need for this protein to occur as a zwitterion with a positive net charge?

any pH < 5.4 (more acidic)

what are some characteristics of renal aminoaciduria

increased urine AA levels

normal plasma AA levels

• caused by a malfunction in renal reabsorption of AA

• can be acquired or congenital

what are some characteristics of overflow aminoaciduria

increased urine AA levels

increased plasma AA levels

• caused by a build up of AA with normal renal clearance

• can be acquired or congenital

what is secondary aminoaciduria 

a defect in renal tubular transport mechanism 

what is primary aminoaciduria

congenital enzyme defect that inhibits the body’s ability to metabolize certain AA

• causes buildup of toxic AA and AA byproducts in blood and urine

what is phenylketonuria (PKU)

• Absence of phenylalanine hydroxylase

• Mousy odor of the urine

• Causes significant brain damage 

• seen typically in babies

what are the 2 types of tyrosinemia

type I: furmarylacetoacetate acid hydrolase (FAH) deficiency

• cabbage-like odor in infants

type II: tyrosine aminotransferase (TAT) deficiency 

what is maple syrup urine disease (MSUD)

absence or reduction of alpha-ketoacid decarboxylase

• odor of maple syrup or burnt sugar in the urine, breath, and skin

what is isovaleric acidemia

absence of isovaleryl-CoA dehydrogenase

• sweaty feet odor of urine due to build up of isovaleric acid 

what is homocystinuria

absence of cystathionine-beta-synthetase

what is alkpatonuria

absence of homogentisic acid oxidase

• urine will appear darkened after exposure to light

what is cystinuria

absence of carrier protein that helps in reabsorption of cysteine, lysine, ornithine, and arginine

• causes buildup of AA in urine and renal calculi formation

what 2 tests can be used for AA acid analysis

blood or urine

what are some of the criteria that must be met for an AA analysis of a peripheral blood sample?

• Heparinized plasma (heparin as anticoagulant)

• Patient should fast for 6-8 hours

• NO WHITE CELLS OR PLATELETS OR HEMOLYSIS!!!

• The sample must be deproteinized within 30 minutes and immediately run or frozen

what are some of the criteria that must be met for an AA analysis of a urine sample?

a random void is acceptable for qualitative analysis. However, a 24-hour urine is needed to complete quantitative testing

what is the dye used to stain AA during a TLC analysis

ninhydrin