Azidodeoxythymidine and didehydrodeoxythymidine as inhibitors and substrates of the human herpesvirus 8 thymidine kinase

• Published in: Journal of antimicrobial chemotherapy 2002-02, Vol.49 (2), p.359-366
• Main Authors: Lock, Matthew J., Thorley, Nicola, Teo, Jeanette, Emery, Vincent C.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Anti-HIV Agents - metabolism; Anti-HIV Agents - pharmacology; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antiviral agents; Biological and medical sciences; Catalytic Domain - genetics; Enzyme Inhibitors - metabolism; Enzyme Inhibitors - pharmacology; Herpesvirus 8, Human - drug effects; Herpesvirus 8, Human - enzymology; Herpesvirus 8, Human - genetics; Herpesvirus 8, Human - isolation & purification; Humans; Kinetics; Male; Medical sciences; Molecular Sequence Data; Pharmacology. Drug treatments; Phosphorylation; Recombinant Proteins - biosynthesis; Recombinant Proteins - genetics; Stavudine - metabolism; Stavudine - pharmacology; Substrate Specificity; Thymidine Kinase - antagonists & inhibitors; Thymidine Kinase - metabolism; Zidovudine - metabolism; Zidovudine - pharmacology
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/49.2.359

Human herpesvirus 8 (HHV-8), the aetiological agent of Kaposi's sarcoma (KS), encodes many core genes that have been maintained during evolution of the Herpesviridae. Among these is a thymidine kinase (TK) homologue (ORF21), which has 12% homology to the related TK encoded by herpes simplex virus. We show that the HHV-8 TK is a functional deoxythymidine (dT) kinase, with Michaelis constants (Km) for dT and ATP of 18.5 and 6.6 μM, respectively. Using homology modelling coupled with site-directed mutagenesis, we identify Gly265, Asp362 and Phe372 as key amino acid residues involved in the catalytic process. The HHV-8 TK is competitively inhibited by azidodeoxythymidine (zidovudine) and didehydrodeoxythymidine (stavudine) and can also accept these anti-retroviral compounds as substrates. These data have implications for our understanding of changes in AIDS-KS incidence following the clinical licensing of these compounds and in the development of new therapies for KS.