Purification and Characterization of a Rat Liver Enzyme That Hydrolyzes Valaciclovir, the L-Valyl Ester Prodrug of Acyclovir

Burnette, Thimysta C.; Harrington, Joan A.; Reardon, John E.; Merrill, Barbara M.; Miranda, Paulo de

doi:10.1074/jbc.270.26.15827

Cited by 46 publications

(25 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…BPHL exhibited stereoselectivity such that it hydrolyzed D-VACV at a much lower rate (specific activity, 28.1 Ϯ 4.26 nmol/min/g of protein with 1 mM D-VACV) than L-VACV (98 Ϯ 17 nmol/min/g of protein with 0.4 mM VACV). This is in agreement with the observed stereoselectivity of the biochemically purified hVACVase and rVACVase (17).…”

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 79%

“…2). Similar to the previous report (17), VACV hydrolytic activity was enriched in the solubilized membrane fraction (MEs), and specific VACV hydrolysis activity was significantly less in other subcellular fractions (data not shown). Therefore, the MEs fraction was used for further biochemical purification.…”

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 77%

“…This hVACVase did not bind to a DEAE anion exchange column at pH 8, suggesting that hVACVase remains positively charged at pH 8. The enrichment of VACV hydrolytic activity in the solubilized membrane fraction and a high pI value are consistent with those observed for rVACVase (17).…”

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 70%

“…Thus, BPHL was purified by anion exchange, hydroxyapatite, and gel filtration column chromatography. BPHL did not bind to the DEAE anion exchange column at pH 7.4, suggesting that BPHL is a basic protein at neutral pH similar to VACVases with a theoretical pI value greater than 8 (17).…”

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-mentioning

confidence: 99%

“…VACV was shown to be relatively stable in gut lumen while very susceptible to intracellular enzymatic hydrolysis (16). In an attempt to identify a VACV-hydrolyzing enzyme, Burnette et al (17) purified and sequenced several peptide fragments of the major polypeptide from a purified preparation of rat VACV hydrolase, a putative novel protein from rat liver. VACV hydrolase in rat liver (rVACVase) was 29 kDa in size and a basic, monomeric protein that seemed to be associated with mitochondria.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Identification of a Human Valacyclovirase

Kim¹,

Chu²,

Kim³

et al. 2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Valacyclovir is the 5-valyl ester prodrug of acyclovir, an effective anti-herpetic drug. Systemic availability of acyclovir in humans is three to five times higher when administered orally as the prodrug. The increased bioavailability of valacyclovir is attributed to carrier-mediated intestinal absorption, via the hPEPT1 peptide transporter, followed by the rapid and complete conversion to acyclovir. The one or more human enzymes responsible for in vivo activation of the prodrug to the active drug and its conversion sites, however, have not been identified. In this report, we describe the purification, identification, and characterization of a human enzyme that activates valacyclovir to acyclovir. A protein with significant hydrolytic activity toward valacyclovir, the 5-glycyl ester of acyclovir, and the 5-valyl ester of zidovudine (AZT), was purified from Caco-2 cells derived from human intestine. Using a non-redundant data base search, the N-terminal 19-amino acid sequence of the purified 27-kDa, basic protein revealed a perfect match within the N terminus of a serine hydrolase, Biphenyl hydrolase-like (BPHL, gi:4757862) protein, previously cloned from human breast carcinoma. Recombinant BPHL exhibited significant hydrolytic activity for both valacyclovir and valganciclovir with specificity constants (k cat /K m ), 420 and 53.2 mM ؊1 ⅐s ؊1 , respectively. We conclude that BPHL may be an important enzyme activating valacyclovir and valganciclovir in humans and an important new target for prodrug design.Prodrugs of therapeutically active agents have been used to improve pharmaceutical, biopharmaceutical, and pharmacokinetic properties of numerous active therapeutic agents. Prodrugs are designed to be inactive until in vivo activation to the parent drug, and hence reliable in vivo activation of the prodrug is considered critical for their pharmacological activity (1). Identification of the mechanism of in vivo activation of prodrugs is important for prodrug design and for investigating clinical applications. Furthermore, design and development of prodrugs for humans has been significantly hampered by the unknown species differences in the activating enzymes. Thus, identification of the one or more prodrug-activating enzymes will significantly aid in the selection of animal models for human drug development.The participation of peptidases or esterases in prodrug activation will depend on the pro-moiety, its linker to the parent drug, as well as the parent drug. For several prodrugs, their in vivo activation mechanism has been studied in more detail. For example, the anti-cancer prodrug, CPT-11 (irinotecan), a carbamate derivative of 7-ethyl-10-hydroxycamptothecin, is converted to its active metabolite, 7-ethyl-10-hydroxycamptothecin by human carboxylesterases. The efficiency of hydrolysis varies depending on isoforms such that carboxylesterase 2 (hCE2) 1 and intestinal carboxylesterase (hiCE) are more efficient activators than human liver carboxylesterase 1 (hCE1) (2-4). The angiotensin-converting enzyme inhibitor...

show abstract

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 79%

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 77%

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-supporting

confidence: 70%

Section: Purification Of Valacyclovir Hydrolase From Caco-2 Cells-mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Identification of a Human Valacyclovirase

Kim¹,

Chu²,

Kim³

et al. 2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

The Biochemistry of Drug Metabolism – An Introduction

Testa

Krämer

2007

Chemistry & Biodiversity

View full text Add to dashboard Cite

This review continues a general presentation of the metabolism of drugs and other xenobiotics begun in two recent issues of Chemistry & Biodiversity. This Part presents some of the numerous hydrolases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the many reactions of hydrolysis they catalyze. A number of medicinally, environmentally, and toxicologically relevant examples are presented and discussed. The reactions examined include the hydrolysis of carboxylic esters, amides and peptides, lactones, and other labile rings, and esters of inorganic acids. The hydration of epoxides and its enzymology are treated separately.

show abstract