Nitrogen and Urea Flashcards
what are zymogens, and what are four different kings
become active enzymes in dietary protein digestion
what is low HCl concentration called and what can it cause?
achlorhydria and it can cause iron deficiency
pancreatic zymogens
(activated by proteolysis)
- trypsinogen > trypsin (by enteropeptidase)
- chymotrypsinogen > chymotrypsin (by trypsin)
- proelastase > elastase (by trypsin)
- procarboxypeptidases > carboxypeptidase A or B –exopeptidase (by tripsin)
which endopeptide amino acids does trypsin cleave?
lysines and arginines
defects in neutral amino acid transport system lead to what, and what is the main source of their symptoms
Hartnup disease–(neutral amidoaciduria) ataxia, emotional instability, pellagra rash)
tryptophan deficiency here is precursor for niacin (B3), and deficiency in niacin responsible for most of the symptoms
where does proteolysis occur intracellularly
in lysosomes (with acid hydrolases, pH of 5 optimal) in cytosol (poly-ubiquitin-tagged proteins degraded by 26S proteasome)
2 types of extracellular proteolyses
serine proteases and matrix metalloproteases (collagenases)
what protease problem occurs in chronic pulmonary disease
elastase (a serine protease) from neutrophils contributes to lung damage
where do nitrogens come from in urea
nitrogen from amino acids goes to aspartate and ammonia which combine in urea cycle (with CO2) to form urea
acute encephalopathy is associated with
hyperammonemia (high ammonium concentration which is very toxic to the nervous system)
aminotransferase catalyze transfer of alpha-amino group from amino acid to alpha-ketoacid with use of what?
pyridoxal phosphate (PLP) from pyridoxine or Vitamin B6–can have too much
note: aldehyde carbon forms schiff base (C=N)
what are used to evaluate liver damage (especially from solvents)
serum alanine aminotransferase (ALT) and asparate aminotransferase (AST)
what occurs in oxidative deamination and where is it located
glutamate dehydrogenase cleaves nitrogen from glutamate to produce alpha-ketoglutarate and ammonium ion (can use NADH or NADPH).
occurs in the liver under when energy low
hydrolytic deamination reduces side chains of what two amide groups
asparagine and glutamine (contain amides)
which two amino acids use nonoxidative deamination and what is this method dependent on
serine (serine dehydratase) and threonine (theonine dehydratase). dehydration precedes deamination, and both use PLP prosthetic group
how is nitrogen transported from muscle to liver
glutamine and alanine transport in blood. glutamine deaminated to glutamate and deaminated again to alpha-ketoglutarate
glutamine synthase
can fix ammonium ion in carbon compound and converts glutamate to glutamine with ATP
4 things oxaloacetate can turn into
- transamination to aspartate
- conversion to glucose
- condensation with acetyl coA to form citrate
- conversion into pyruvateq
high levels of glutamine in brain cause
osmotic increase in H2O in astroytes and get brain swelling. incr. glutamine causes decrease in neurotransmitters glutamate and GABA
shift of equilibrium of glutamate dehydrogenase may cause
depleted alpha-ketoglutarate (essential for TCA) resulting in decr oxidation and ATP
(hyperammonemia particularly bad for brain because depends on TCA for energy)
treatment for defects in urea cycle
hemodialysis/transfusion (for acute)
limit protein in diet, high carb
remove excess ammonia (take levulose, avoid infections, kill intestinal ammonia w/ antibiotics. benzoate to reduce glutamine
replace intermediates (supp with arginine or citrulline)
circumventing ways to remove urea
glycine removed by benzoic acid and glutamine removed by phenybutyrate
ornithine transcarbamylase deficiency
x-linked trait causes hyperammonemia and in male infants, explosive neonatal hyperammonemia
what Jesse Gelsinger had
