Amino-acid catabolism, urea cycle, de-novo purine/pyrimidine biosynthesis, one-carbon metabolism.
Amino Acid And Nucleotide Metabolism
Transamination
α-Amino group transfer from amino acid to α-ketoglutarate (→ glutamate) by aminotransferases using pyridoxal-phosphate cofactor. Central to…
Urea cycle
Five-step hepatic cycle converting toxic ammonia + aspartate → urea (ureotelic nitrogen excretion). Split between mitochondria (CPS1, OTC)…
De-novo purine biosynthesis
Ten-step assembly of IMP on PRPP scaffold, incorporating Gly, Gln, Asp, and formyl-THF. IMP branches to AMP (via adenylosuccinate) and GMP…
De-novo pyrimidine biosynthesis
Six-step biosynthesis of UMP from carbamoyl-P + aspartate (via CAD complex + DHODH + UMPS). UMP → UTP → CTP; dUMP → dTMP by thymidylate…
Nucleotide salvage
Recycling free bases/nucleosides to nucleotides via HGPRT, APRT, TK, DCK, adenosine kinase. HGPRT deficiency → Lesch-Nyhan syndrome.
Folate one-carbon metabolism
Tetrahydrofolate (THF) carries one-carbon units (methyl, methylene, formyl) for thymidylate, purine, and methionine synthesis. Vitamin-B9…
Ketogenic vs glucogenic amino acids
Degradation products enter either ketone-body pathway (Leu, Lys — pure ketogenic) or gluconeogenesis (Ala, Gly, Ser — pure glucogenic).…
Essential amino acids
Nine amino acids humans cannot synthesise: His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val. Must be obtained from diet. Limiting amino acid in…
Purine salvage (HGPRT)
Hypoxanthine-guanine phosphoribosyltransferase recycles purine bases to nucleotides. Deficiency → Lesch-Nyhan syndrome (hyperuricemia,…
Ammonia detoxification
Hepatic urea cycle (humans); glutamine synthesis (brain, muscle); uric acid excretion (birds, reptiles). Hyperammonemia → hepatic…
Urea cycle (ornithine cycle) framework
Krebs-Henseleit 1932: 5-step cycle in liver mitochondria + cytoplasm converting NH₃ + CO₂ + aspartate → urea + fumarate. Net…
Purine de-novo biosynthesis (IMP pathway) framework
10-step pathway from PRPP (5-phospho-ribose-1-pyrophosphate) → IMP using glycine, glutamine, aspartate, formate (via…
Urea cycle (Krebs-Henseleit 1932)
Krebs-Henseleit 1932 5-step urea-cycle; modern OTC + arginase deficiencies + ammonia toxicity.
Transamination (Schlenk 1942)
Schlenk 1942 + Snell 1944 PLP-pyridoxal transaminase mechanism; modern aspartate-aminotransferase + alanine-transaminase clinical-markers.
Purine de novo (Buchanan 1958)
Buchanan-Hartman 1958 11-step de-novo purine biosynthesis; modern target for chemotherapy methotrexate + 6-MP.
Pyrimidine de novo (Jones 1980)
M E Jones 1980 6-step pyrimidine biosynthesis; CAD multi-domain enzyme; modern leflunomide DHODH-inhibitor immunosuppressant.
Salvage / HGPRT (Lesch-Nyhan)
Lesch-Nyhan 1964 HGPRT-deficiency; modern allopurinol + pegloticase for hyperuricemia + gout.
Essential AAs (Rose 1957)
W Rose 1957 9 essential amino-acids in human nutrition; modern Diamond-Inohara 2014 mTORC1-leucine sensing.
Urea cycle (Krebs-Henseleit 1932)
H Krebs-K Henseleit 1932 (Nobel 1953) urea-cycle; modern modern foundational text + ammonia-detoxification + UCD+OTC inborn-errors.
Essential AA (Rose 1957)
W Rose 1957 essential-amino-acids; modern modern foundational text + Rose-classification + 2024 plant-based protein adequacy +…
Salvage pathway (Kornberg 1955)
A Kornberg 1955 (Nobel 1959) nucleotide-salvage HGPRT; modern modern foundational text + Lesch-Nyhan + thiopurine-pharmacogenomics.
De-novo purine (Buchanan 1948)
J Buchanan 1948 de-novo-purine; modern modern foundational + 5-FU + methotrexate cancer-chemo + 2024 IMPDH-inhibitor mizoribine RA.
Transamination (Braunstein 1937)
A Braunstein-M Kritzmann 1937 transamination + Snell 1945 PLP; modern modern foundational text + B6-deficiency + Quinolinate kynurenine…
tRNA-synthetase (Fersht 1977)
A Fersht 1977 + Schimmel 1995 tRNA-synthetase fidelity; modern modern foundational text + editing + nicotinamide + 2024 paralogous…