Abstract
S-adenosylhomocysteine hydrolase (AdoHcyase) catalyzes the hydrolysis of AdoHcy to adenosine and homocysteine. Increased levels of AdoHcy may play a role in the development of cardiovascular diseases and numerous other conditions associated with hyperhomocysteinemia. Several polymorphic isoforms named SAHH-1 to 4 may be resolved by horizontal starch gel electrophoresis from red blood cells. We have identified the genetic background of isoforms SAHH-2 and SAHH-3. SAHH-2 represents the previously described polymorphism in exon 2 of the AdoHcyase gene (112 C>T; p.R38W). Isoform SAHH-3 is based on a new polymorphism in exon 3 (377 G>A), leading to the conversion of glycine to arginine at amino-acid position 123. To shed light on the effects of these polymorphisms on the molecular and catalytic properties of AdoHcyase, we made recombinant wild-type and polymorphic R38W and G123R enzymes for a comparative analysis. The amino-acid exchanges did not bring about major changes to the catalytic rates of the recombinant proteins. However, circular dichroism analysis showed that both polymorphisms effect the thermal stability of the recombinant protein in vitro, reducing the unfolding temperature by approximately 2.6°C (R38W) and 1.5°C (G123R) compared to wild-type protein. In view of the altered thermal stability, and slightly decreased enzymatic activity of polymorphic proteins (≤6%), one may consider the analyzed AdoHcyase isoforms as risk markers for diseases caused by irregular AdoHcyase metabolism.
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Acknowledgements
This work was supported by Grants 0098086 (OV) and 0108016 (KF, MC, IB) of the Ministry of Science, Education and Sports from the Republic of Croatia and by the Austrian Science Fund (FWF) project P17885 (TP). We thank Drs Dorotea Dorčić and Danijela Petković for help in collecting the samples and information of studied individuals. We are extremely grateful to Vesna Musani for supervision of the sequencing core facility at the Ruđer Bošković Institute. We greatly appreciate the commitment of participants and their informed consent regarding this study.
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Fumić, K., Belužić, R., Ćuk, M. et al. Functional analysis of human S-adenosylhomocysteine hydrolase isoforms SAHH-2 and SAHH-3. Eur J Hum Genet 15, 347–351 (2007). https://doi.org/10.1038/sj.ejhg.5201757
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DOI: https://doi.org/10.1038/sj.ejhg.5201757
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