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| What is the major precursor of the biosynthesis of porphyrins? (Porphyrins are of central importance in heme proteins such as hemoglobin & the cytochromes) |
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| the monopyrrol derivative from which 4 molecules come together to construct porphyrins; derived from two molecules of delta-aminolevulinate |
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| what forms when 4 molecules of porphobilinogen (each porphobilinogen is formed when two molecules of delta-aminolevulinate condense) come together through a series of complex enzymatic reactions |
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| the collective variety of human diseases caused by genetic defects in the biosynthesis of porphyrins which leads to the accumulation of pathway intermediates |
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| yielded (along with free Fe2+) when the iron-porphyrin group of hemoglobin is released from dying erythrocytes in the spleen & degraded |
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| an important energy buffer in skeletal muscle which is derived from creatine |
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| a redox buffer that is present in plants, animals, & some bacteria |
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| an enzyme that contains a covalently bound selenium atom in the form of selenocysteine which is essential for its activity |
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| used to treat tuberculosis |
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| a rigid polymer; derived from phenylalanine & tyrosine & is second only to cellulose in abundance in plant tissues |
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| the plant growth hormone "indole-3-acetate" for which tryptophan is the precursor; important in the regulation of a wide range of biological processes in plants |
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| 3 catecholamines that come from tryptophan |
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Definition
1. dopamine
2. norepinephrine
3. epinephrine |
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| a neurotransmitter; derived from tryptophan in a two-step pathway |
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| formed from the decarboxylation of histidine; a powerful vasodilator in animal tissues |
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| the histamine receptor antagonist; a structural analog of histamine |
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| 2 polyamines involved in DNA packaging that are derived from methionine & ornithine |
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| a PLP-requiring enzyme which is the target of several powerful inhibitors used as pharmaceutical agents |
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| 2 types of pathways that lead to nucleotides |
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Definition
1. de novo pathways
2. salvage pathways |
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| what the pyrimidine ring is synthesized as for nucleotide biosynthesis; it is attached to ribose phosphate & then converted to the common pyrimidine nucleotides required in nucleic acid synthesis |
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| sequential feedback inhibition |
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Definition
| when both products of purine nucleotide biosynthesis are present in sufficient quantities, IMP builds up & it inhibits an earlier step in the pathway; a regulatory strategy |
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Term
| carbamoyl phosphate synthetase II |
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Definition
| the enzyme in the cytosol that makes the carbamoyl phosphate required in pyrimidine biosynthesis (unlike carbamoyl phosphate synthetase I, which makes the carbamoyl phosphate required in urea synthesis in animals in mitochondria) |
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Definition
| catalyzes the reaction in which water is removed from N-carbamoylaspartate; causes the pyrimidine ring to close to form L-dihydoorotate |
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| forms CTP from UTP; works by way of an acyl phosphate intermediate |
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| promotes phosphorylation of AMP to ADP |
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Term
| nucleoside monophosphate kinases |
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Definition
| a class of enzymes which allows for ATP to bring about the formation of nucleoside diphosphates |
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| nucleoside diphosphate kinase |
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Definition
| a ubiquitous enzyme that allows for nucleoside diphosphates to be converted to triphosphates |
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| an enzyme best characterized in E. coli in which its substrates are ribonucleoside diphosphates |
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| an intermediate hydrogen-carrying protein which allows NADPH to donate a pair of hydrogen atoms to the reaction in which the D-ribose portion of a ribonucleoside diphosphate is reduced to 2'-deoxy-D-ribose |
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| catalyzes the reaction in which the oxidized form of thioredoxin is reduced by NADPH; reduced thioredoxin is then used by ribonucleotide reductase to reduce the nucleoside diphosphates to deoxy-ribonucleoside diphosphates |
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| a protein (closely related to thioredoxin) which uses glutathione as the reductant; transfers the reducing power to ribonucleotide reductase |
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| catalyzes the conversion of dUMP to dTMP |
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| reduces dihydro-folate to tetrahydrofolate; this regeneration is essential for the many processes that require tetrahydrofolate |
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Definition
| allows for purine nucleotides to be degraded by a pathway in which they lose their phosphate |
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| deaminates adenosine (yielded from adenylate) to inosine; inosine is then hydrolyzed to hypoxanthine & D-ribose |
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| oxidizes hypoxanthine to xanthine & then uric acid; a flavoenzyme with an atom of molybdenum & four iron-sulfur centers in its prosthetic group |
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| What is the relationship between allantoin & urate oxidase? |
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Definition
| uric acid is degraded to allantoin by urate oxidase in most mammals & many other vertebrates |
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Term
| adenosine deaminase (ADA) deficiency |
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Definition
| leads to severe immunodeficiency disease in which T lymphocytes & B lymphocytes do not develop properly |
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Term
| adenosine phosphoribosyltransferase |
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Definition
| catalyzes one of the primary salvage pathways; allows for free adenine to react with PRPP to yield the corresponding adenine nucleotide |
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| hypoxanthine-guanine phosphoribosyltransferase |
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Definition
| salvages free guanine & hypoxanthine |
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| a genetic lack of hypoxanthine-guanine phosphoribosyltransferase activity (seen almost exclusively in male children) |
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| a drug; inhibits xanthine oxidase (the enzyme that catalyzes the conversion of purines to uric acid) |
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| an inhibitor that acts on thymidylate synthase; an important chemotherapeutic agent |
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| a prominent chemotherapeutic agent; an inhibitor of dihydrofolate reductase |
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| an antibiotic developed by Hitchings & Elion which binds to bacterial dihydrofolate reductase nearly 100,000 times better than to the mammalian enzyme |
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| how the metabolic processes of different species function in the biosphere to salvage & reuse biologically available nitrogen |
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| the process in which bacteria reduce nitrate to N2 under anaerobic conditions to maintain the balance between fixed nitrogen & atmospheric nitrogen |
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| the anaerobic ammonia oxidation promoted by a group of bacteria which short-circuit the nitrogen cycle; a process that convert ammonia & nitrate to N2 |
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Term
| What is the relationship between nitrate reductase & nitrite reductase? |
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Definition
| NO3- is reduced to NO2- by nitrate reductase & then the NO2- is reduced to NH4+ in a six-electron transfer catalyzed by nitrite reductase |
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| What is the relationship between nitrogenase complex & dinitrogenase reductase/dinitrogenase? |
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Definition
| biological nitrification is carried out by a highly conserved complex of proteins (the nitrogenase complex); its central components are dinitrogenase reductase & dinitrogenase |
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| a cofactor in dinitrogenase; a novel structure composed of 7 Fe atoms, 9 inorganic S atoms, a Cys side chain, & a single carbon atom in the center of the FeS cluster |
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| the reduced form plays a role in the immediate source of electrons to reduce dinitrogenase reductase; works with reduced flavodoxin |
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| the oxygen-binding heme protein in which the bacteria in root nodules are bathed to solve the oxygen-toxicity problem; produced by the plant |
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| catalyzes the reaction of glutamate & NH4+ to yield glutamine |
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| catalyzes the reaction in bacteria & plants which produces glutamate from glutamine |
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| promotes both adenylylation & deadenylylation; part of a complex enzymatic cascade that responds to levels of glutamine, alpha-ketoglutarate, ATP, & Pi |
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| the enzyme that brings about both uridylylation & deuridylylation of PII |
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| must be obtained from food |
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Term
| 5-phosphoribosyl-1-pyrophosphate (PRPP) |
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Definition
| a notable intermediate in several pathways of amino acid & nucleotide synthesis in addition to the 6 precursors |
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Term
| ribose phosphate pyrophosphokinase |
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Definition
| catalyzes the reaction in which PRPP is formed from ribose 5-phosphate derived from the pentose phosphate pathway |
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| a cyclic derivative of glutamate |
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Definition
| synthesizes from glutamate via ornithine & the urea cycle in animals |
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Term
| ornithine delta-aminotransferase |
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Definition
| the enzyme that converts ornithine to glutamate gamma-semialdehyde |
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Term
| What is the relationship between glycine & serine hydroxymethyltransferase? |
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Definition
| serine is the precursor of glycine through the removal of a carbon atom by serine hydroxymethyltransferase |
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Definition
| synthesized by amidation of aspartate with glutamine donating the NH4+ |
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Term
| 3 amino acids which aspartate gives rise to |
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Definition
1. methionine
2. threonine
3. lysine |
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