Gammaherpesviruses encode functional dihydrofolate reductase activity

• Published in: Biochemical and biophysical research communications Vol. 297; no. 4; pp. 756 - 759
• Main Authors: Gáspár, Gábor, De Clercq, Erik, Neyts, Johan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04.10.2002
• Subjects: Animals; Cloning, Molecular; Cytomegalovirus - enzymology; Cytomegalovirus - genetics; Escherichia coli - enzymology; Gammaherpesvirinae - enzymology; Gammaherpesvirinae - genetics; Herpesvirus 8, Human - enzymology; Herpesvirus 8, Human - genetics; Humans; Kinetics; Mice; Recombinant Proteins - metabolism; Tetrahydrofolate Dehydrogenase - genetics; Tetrahydrofolate Dehydrogenase - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(02)02286-6

We overexpressed and purified from Escherichia coli the dihydrofolate reductase (DHFR) of the gammaherpesviruses human herpesvirus 8 (HHV-8), herpesvirus saimiri (HVS), and rhesus rhadinovirus (RRV). All three enzymes proved catalytically active. The K m value of HHV-8 DHFR for dihydrofolate (DHF) was 2.02±0.44 μM , that of HVS DHFR was 4.31±0.56 μM , and that of RRV DHFR is 7.09±0.11 μM . These values are approximately 5–15-fold higher than the K m value reported for the human DHFR. The K m value of HHV-8 DHFR for NADPH was 1.31±0.23 μM , that of HVS DHFR was 3.78±0.61 μM , and that of RRV DHFR was 7.47±0.59 μM . These values are similar or slightly higher than the corresponding K m value of the human enzyme. Methotrexate, aminopterin, trimethoprim, pyrimethamine, and N(α)-(4-amino-4-deoxypteroyl)-N(δ)-hemiphthaloyl- l-ornithine (PT523), all well-known folate antagonists, inhibited the DHFR activity of the three gammaherpesviruses competitively with respect to DHF but proved markedly less inhibitory to the viral than towards the human enzyme.