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Dephosphorylation of MnDPDP and related compounds by acid and alkaline phosphatase

K G Toft1, A H Myrset, T Skotland

  • 1Nycomed Imaging AS, Research and Development, P.O. Box 4220 Nydalen, N-0401, Oslo, Norway. kim.gunnar.toft@no.nycomed-amersham.com

Journal of Pharmaceutical and Biomedical Analysis
|May 30, 2001
PubMed

Insights

Alkaline phosphatase is significantly more active than acid phosphatase in dephosphorylating the MRI contrast agent Teslascan (MnDPDP) and its metabolites. This indicates alkaline phosphatase plays a major role in the in vivo metabolism of Teslascan.

Area of Science:

  • Biochemistry
  • Pharmacology
  • Medical Imaging

Background:

  • Teslascan (MnDPDP) is a magnetic resonance imaging contrast agent.
  • Understanding its metabolic pathways is crucial for clinical application.
  • Enzymatic dephosphorylation is a key metabolic process.

Purpose of the Study:

  • To investigate the in vitro enzymatic dephosphorylation of Teslascan (MnDPDP) and its zinc analog (ZnDPDP).
  • To compare the activity of acid phosphatase and alkaline phosphatase in this process.
  • To determine the primary enzyme responsible for Teslascan metabolism in vivo.

Main Methods:

  • In vitro enzymatic assays using acid phosphatase (human prostatic) and alkaline phosphatase (human placental).
  • Dephosphorylation of MnDPDP and ZnDPDP to monophosphate (MnDPMP, ZnDPMP) and fully dephosphorylated (MnPLED, ZnPLED) forms.
  • Enzyme kinetic comparisons between acid and alkaline phosphatases.

Main Results:

  • Both acid and alkaline phosphatases dephosphorylated MnDPDP and ZnDPDP to MnDPMP/ZnDPMP and MnPLED/ZnPLED.
  • Alkaline phosphatase exhibited approximately four times higher activity than acid phosphatase for both MnDPDP and ZnDPDP.
  • Similar activity differences were observed for the monophosphate metabolites.

Conclusions:

  • Alkaline phosphatase is significantly more efficient in dephosphorylating Teslascan and its metabolites compared to acid phosphatase.
  • Given the higher activity of alkaline phosphatase in serum, it is likely responsible for the majority of Teslascan dephosphorylation in vivo.
  • These findings provide insight into the pharmacokinetic profile of Teslascan.

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