The plasmid was introduced into a yeast histidine auxotroph (i.e.

We will look at this pathway in a bit more detail, because it involves themolecule 5-phosphoribosyl--pyrophosphate (which wewill refer to as "PRPP" from now on). PRPP is also involved in thesynthesis of purines and pyrimidines, as we will soon see. In the first step ofhistidine synthesis, PRPP condenses with ATP to form a purine, N1-5'-phosphoribosylATP, in a reaction that is driven by the subsequent hydrolysis of thepyrophosphate that condenses out. Glutamine again plays a role as an amino groupdonor, this time resulting in the formation of 5-aminoamidazole-4-carboximideribonucleotide (ACAIR), which is an intermediate in purine biosynthesis.

We have found cross-pathway regulation between purine and histidinebiosynthesis in yeast.

FIGURE 15–9 Interlocking regulatory mechanisms in the biosynthesisof several amino acids derived from aspartate in E. coli. Threeenzymes (A, B, C) have either two or three isozyme forms, indicatedby numerical subscripts. In each case, one isozyme (A2, B1, and C2)has no allosteric regulation; these isozymes are regulated by changesin the amount synthesized. Synthesis of isozymes A2 andB1 is repressed when methionine levels are high, and synthesis ofisozyme C2 is repressed when isoleucine levels are high. Enzyme Ais aspartokinase; B, homoserine dehydrogenase; C, threonine dehydratase.


Regulation of Histidine Biosynthesis in Salmonella Typhimurium

From the effects of adenine and histidine on tubercidin biosynthesis in S.

Metabolism1.0 Global and overview maps1.1 Carbohydrate metabolism1.2 Energy metabolism1.3 Lipid metabolism1.4 Nucleotide metabolism1.5 Amino acid metabolism1.6 Metabolism of other amino acids1.7 Glycan biosynthesis and metabolism1.8 Metabolism of cofactors and vitamins1.9 Metabolism of terpenoids and polyketides1.10 Biosynthesis of other secondary metabolites1.11 Xenobiotics biodegradation and metabolism1.12 Chemical structure transformation maps


and the possible regulation of histidine transport.

FIGURE 15–10 Biosynthesis of δ-aminolevulinate. (a) In mammalsand other higher eukaryotes, δ-aminolevulinate is synthesized fromglycine and succinyl-CoA. The atoms furnished by glycine are shownin red. (b) In bacteria and plants, the precursor of δ-aminolevulinateis glutamate. (c) Biosynthesis of heme from δ-aminolevulinate.

ASMscience | Biosynthesis and Regulation of the …

In addition to their role as the building blocks of proteins,amino acids are precursors of many specialized biomolecules,including hormones, coenzymes, nucleotides,alkaloids, cell wall polymers, porphyrins, antibiotics,pigments, and neurotransmitters. We describe here thepathways to a number of these amino acid derivatives.

Biosynthesis and Regulation of the Branched-Chain Amino ..

has 3 isozymes of aspartokinase that respond differently toeach of the 3 amino acids, with regard to enzyme inhibition and feedbackinhibition. The biosynthesis of lysine, methionine and threonine are not, then,controlled as a group.

Regulation of biosynthesis and transport of aromatic …

Watanabe T, Taguchi Y, Shiosaka S et al. (1984) Distribution of the histaminergic neuron system in the central nervous system of rats; a fluorescent immunohistochemical analysis with histidine decarboxylase as a marker. Brain Research 295: 13–25.

Genetic dissection of histidine biosynthesis in …

Plants and bacteria synthesize all 20 common amino acids. Mammals cansynthesize about half; the others are required in the diet (essential aminoacids). Among the nonessential amino acids, glutamate is formed byreductive amination of α-ketoglutarate and serves as the precursor of glutamine,proline, and arginine. Alanine and aspartate (and thus asparagine) are formedfrom pyruvate and oxaloacetate, respectively, by transamination. The carbonchain of serine is derived from 3-phosphoglycerate. Serine is a precursor ofglycine; the β-carbon atom of serine is transferred to tetrahydrofolate. Inmicroorganisms, cysteine is produced from serine and from sulfide produced bythe reduction of environmental sulfate. Mammals produce cysteine from methionineand serine by a series of reactions requiring S-adenosylmethionine andcystathionine. Among the essential amino acids, the aromatic amino acids(phenylalanine, tyrosine, and tryptophan) form by a pathway in which chorismateoccupies a key branch point. Phosphoribosyl pyrophosphate is a precursor oftryptophan and histidine. The pathway to histidine is interconnected with thepurine synthetic pathway. Tyrosine can also be formed by hydroxylation ofphenylalanine (and thus is considered conditionally essential). The pathways forthe other essential amino acids are complex. The amino acid biosyntheticpathways are subject to allosteric end-product inhibition; the regulatory enzymeis usually the first in the sequence. Regulation of the various syntheticpathways is coordinated.