Identification of dihydrofolate reductase in rabbit brain

Spector, Reynold; Levy, P. R.; Abelson, Herbert T.

doi:10.1016/0006-2952(77)90423-3

Cited by 29 publications

(6 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The highest expression of DHFR was found in the brain among all tissues examined. This is in contrast to the previous reports for rabbit that DHFR activity in brain extracts was only 10 to 18% of that in liver extracts (Spector et al, 1977). This difference might reflect the variation among species.…”

Section: Discussioncontrasting

confidence: 99%

Characterization and Comparative Studies of Zebrafish and Human Recombinant Dihydrofolate Reductases—Inhibition by Folic Acid and Polyphenols

Kao¹,

Wang

Chang

et al. 2007

Drug Metab Dispos

View full text Add to dashboard Cite

ABSTRACT:Dihydrofolate reductase (DHFR) catalyzes folic acid reduction and recycles dihydrofolate generated during dTMP biosynthesis to tetrahydrofolate. DHFR is the main target of methotrexate, the most widely used agent for antifolate therapy. Nevertheless, the emergence of methotrexate-resistance has greatly impeded the curative potential of this drug. Therefore, drugs with improved efficacy are still in demand, as well as an efficient in vitro assay system and animal model for antifolate drug discovery. The aim of this study is to evaluate the suitability of using zebrafish DHFR as an alternative assay system for antifolate drug discovery. The cDNAs encoding zebrafish and human DHFR were cloned, overexpressed, and purified. Similar structural and kinetic properties were revealed between zebrafish and human recombinant DHFRs. The susceptibilities of both enzymes to known DHFR inhibitors, including methotrexate and trimethoprim, and compounds with antifolate potential, such as polyphenols, are also comparable. In addition, the DHFR-mediated dihydrofolate reduction was significantly inhibited by its own substrate folic acid. An unexpected tissuespecific distribution of DHFR was observed with the highest level present in ova and brains of zebrafish. DHFR is also abundant in zebrafish embryos of early stages and decreased abruptly after 3 days postfertilization. The substantial resemblance between zebrafish and human DHFRs, as demonstrated in this study, provides compelling evidence supporting the use of zebrafish DHFR as an in vitro assay system for folate-related studies and drug discovery.

show abstract

Section: Discussioncontrasting

confidence: 99%

Characterization and Comparative Studies of Zebrafish and Human Recombinant Dihydrofolate Reductases—Inhibition by Folic Acid and Polyphenols

Kao¹,

Wang

Chang

et al. 2007

Drug Metab Dispos

View full text Add to dashboard Cite

show abstract

“…The presence of both TS and dihydrofolate reductase (Spector et al, 1977) in adult mammalian brain has many important implications. For example, the mechanism of the heretofore poorly understood but serious central nervous system toxicity (Chabner et al, 1975) of the important antineoplastic agents methotrexate, which inhibits dihydrofolate reductase and secondarily TS (Blakely, 1969), and 5-fluorouracil.…”

Section: Discussionmentioning

confidence: 99%

Identification, Development, and Regional Distribution of Thymidylate Synthetase in Adult Rabbit Brain

Suleiman

Spector

1982

Journal of Neurochemistry

Self Cite

View full text Add to dashboard Cite

The development and regional distribution of thymidylate synthetase (TS) (EC 2.1.1.45) in rabbit brain were determined. After optimization of the assay for brain, TS activity in brain was measured by a nonspecific (3H2O release) and specific method. The specific method involved the conversion of [6-3H]deoxyuridine monophosphate (dUMP) to [3H]thymidine phosphate and the subsequent identification of [3H]thymidine.l The specific activity of the enzyme in whole brain of newborn rabbits declined from 10.35 +/- 1.17 units/mg protein to 0.71 +/- 0.09 units/mg protein at 10-12 weeks of age. Two=year-old rabbits had 0.81 +/- 0.04 units/mg protein. The decline in specific activity with age was not due to an inhibitor of TS activity or a change in the Km for dUMP. The Km for dUMP of the unpurified enzyme in the brains of both 19-day-old and young adult rabbits was 0.8 microM. In young adult rabbits (3 months) the specific activity of TS was similar in the various regions of the brain tested except for the cerebellum, which had 40% higher specific activity than the whole brain. The results show that TS is widely distributed in adult rabbit brain, and, although the activity declines with age, it stabilizes at adult levels at 3 months of age.

show abstract

“…In those studies, reserpine evoked both short-term (30-40% within 4 h) and long-term (fivefold at 24 h) effects analogous to its biphasic influence on nigrostriatal TOH activity in homogenates (Segal et al, 1971 ;Sullivan et al, 1972). Slow recovery of BH, may also proceed through the action of a scavenger enzyme, dihydrofolate reductase, which has demonstrated capacity to regenerate reductively nonquinoid BH2 in brain (Spector et al, 1977;Pollock and Kaufman, 1978;Bullard et al, 1979).…”

Section: Discussionmentioning

confidence: 99%