Recent Topics in Pyridoxal 5'-Phosphate Enzyme Studies

Hayashi, Hideyuki; Wada, Hiroshi; Yoshimura, Teizo; Esaki, Nobuyoshi; Soda, Kenji

doi:10.1146/annurev.bi.59.070190.000511

Cited by 94 publications

(56 citation statements)

References 49 publications

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“…The 85% identity of DadX protein to DadB catabolic alanine racemase of S. typhimurium confirms a homology previously proposed because of similar function and location of genes (57,59). The active center of DadX and the Gly-rich hinge known to be important for the catalytic efficiency of alanine racemases have the same structure as in other enzymes of this group and are located at the same position as in DadB (18,22).…”

Section: Resultssupporting

confidence: 82%

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Organization and expression of the Escherichia coli K-12 dad operon encoding the smaller subunit of D-amino acid dehydrogenase and the catabolic alanine racemase

et al. 1994

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A fragment of the Escherichia coli K-12 chromosome complementing the D-amino acid dehydrogenase and catabolic alanine racemase deficiency of a dad operon deletion mutant was cloned in a mini-Mu plasmid. The dadA and dadA genes were localized to a 3.5-kb part of the plasmid insert. The nucleotide sequence of this fragment revealed two open reading frames encoding 432-and 356-amino-acid-long proteins. We show here that they correspond to the dadA and dadX genes. The dadA gene can encode only the smaller of the two subunits of D-amino acid dehydrogenase. A computer search revealed the presence of a flavin adenine dinucleotide-binding motif in the N-terminal domain of the deduced DadA protein sequence. This is in agreement with biochemical data showing that the D-amino acid dehydrogenase contains flavin adenine dinucleotide in its active center. The predicted dadX gene product appeared to be 85% identical to a dadB-encoded catabolic alanine racemase of SalnoneUla typhimurium. The organization of the dadA and dadX genes confirmed our previous conclusion based on the genetic data (J. Wild, J. Hennig, M. Lobocka, W. Walczak, and T. Klopotowski, Mol. Gen. Genet. 198:315-322, 1985) that these genes form an operon. The main transcription start points of the dad operon were determined by primer extension. They are preceded by a putative Cr70 promoter sequence and two cyclic AMP-cyclic AMP receptor protein (cAMP-CRP) binding sites, one of higher and one of lower affinity to CRP. We propose that the high-affinity site, centered 59.5 bp upstream of the main transcription start point, plays a role in cAMP-CRP-mediated activation of dad operon expression in the absence of glucose.

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Section: Resultssupporting

confidence: 82%

“…5) (3). As in other alanine racemases, it contains a lysine residue that interacts directly with pyridoxal phosphate (22). Galactos and Walsh (17) have shown that both alanine racemases of S. typhimurium, catabolic and anabolic, have a two-domain structure.…”

Section: Resultsmentioning

confidence: 99%

Organization and expression of the Escherichia coli K-12 dad operon encoding the smaller subunit of D-amino acid dehydrogenase and the catabolic alanine racemase

et al. 1994

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“…Many enzymes, particularly those involved in amino acid metabolism, require pyridoxal phosphate as a cofactor for activity (46). It is interesting to note that an antibody against pyridoxal phosphate detects low levels of many different proteins in both normal and tumor cell extracts, but the signal from a ϳ50-kDa polypeptide with a pI of ϳ7.0 is greatly amplified in tumor cells (38).…”

Section: Figmentioning

confidence: 99%

Mimosine Targets Serine Hydroxymethyltransferase

Lin

Falchetto

Mosca

et al. 1996

Journal of Biological Chemistry

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The plant amino acid, mimosine, is an extremely effective inhibitor of DNA replication in mammalian cells (Mosca, P. J., Dijkwel, P. A., and Hamlin, J. L. (1992) Mol. Cell. Biol. 12, 4375-4383). Mimosine appears to prevent the formation of replication forks at early-firing origins when delivered to mammalian cells approaching the G 1 /S boundary, and blocks DNA replication when added to S phase cells after a lag of ϳ2.5 h. We have shown previously that [ 3 H]mimosine can be specifically photocross-linked both in vivo and in vitro to a 50-kDa polypeptide (p50) in Chinese hamster ovary (CHO) cells. In the present study, six tryptic peptides (58 residues total) from p50 were sequenced by tandem mass spectrometry and their sequences were found to be at least 77.5% identical and 96.5% similar to sequences in rabbit mitochondrial serine hydroxymethyltransferase (mSHMT). This assignment was verified by precipitating the [ 3 H]mimosine-p50 complex with a polyclonal antibody to rabbit cSHMT. The 50-kDa cross-linked product was almost undetectable in a mimosine-resistant CHO cell line and in a CHO gly ؊ cell line that lacks mitochondrial, but not cytosolic, SHMT activity. The gly ؊ cell line is still sensitive to mimosine, suggesting that the drug may inhibit both the mitochondrial and the cytosolic forms. SHMT is involved in the penultimate step of thymidylate biosynthesis in mammalian cells and, as such, is a potential target for chemotherapy in the treatment of cancer.Our laboratory's interest is the regulation of DNA synthesis in mammalian cells and, in particular, the nature of origins of replication. Although it is known that mammalian DNA is replicated from bidirectional origins spaced ϳ100 kilobase pairs apart (1), the molecular mechanisms of this process remain elusive (see Ref. 2, for review).In the absence of a viable assay for identifying the genetic elements (replicators) that control initiation in mammalian cells, attention has been focussed on determining the positions at which replication initiates, which should lie close to replicators. This approach requires methods for obtaining cell populations in which initiation at a given origin is occurring at the same time. In a commonly used synchronization protocol, cells are first arrested in the G 0 (non-proliferating) compartment by nutritional or serum starvation, followed by release into an inhibitor of DNA synthesis (e.g. Refs. 3-5). The drug treatment is enforced for a time long enough to allow all cells in the population to arrive at the beginning of the S period (a time when at least some origins are sure to be firing); the drug is then removed, allowing cells to enter S in a semi-synchronous wave. Unfortunately, this protocol is not entirely satisfactory for examining initiation events at the beginning of S, because even the most efficacious replication inhibitors do not inhibit initiation per se; rather, they slow the rate of replication fork movement by affecting DNA polymerases (e.g. aphidicolin (6)) or by lowering deoxyribonucleotide pools (e.g. hy...

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“…One hint as to how variations in the level of synthesis of B6-dependent enzymes may be regulated by the cofactors is the observation that induction of the hepatic tyrosine aminotransferase by glucocorticoids is inversely correlated to the intracellular concentration of pyridoxal phosphate (46)(47)(48). During recent years, several cDNA and genomic clones encoding pyridoxal phosphate enzymes have been isolated and characterized (for a review see (49)) which will lead to a better understanding of how pyridoxal phosphate is involved in their expression.…”

Section: Eukaryotesmentioning

confidence: 99%

Regulation of Gene Expression by Cofactors Derived from B Vitamins.

Brandsch

1994

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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SummaryVitamins represent precursor molecules for the majority of cofactors essential for various enzyme activities. Is the expression of proteins that require a specific cofactor for their function correlated to its availability? Examples are presented and discussed of the involvement of vitamin-derived cofactors in the regulatory mechanisms controlling gene expression in bacteria and eukaryotes at the transcriptional and trans lational level.

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Recent Topics in Pyridoxal 5'-Phosphate Enzyme Studies

Cited by 94 publications

References 49 publications

Organization and expression of the Escherichia coli K-12 dad operon encoding the smaller subunit of D-amino acid dehydrogenase and the catabolic alanine racemase

Organization and expression of the Escherichia coli K-12 dad operon encoding the smaller subunit of D-amino acid dehydrogenase and the catabolic alanine racemase

Mimosine Targets Serine Hydroxymethyltransferase

Regulation of Gene Expression by Cofactors Derived from B Vitamins.

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