RESUMEN
Elevated plasma levels of lipoprotein-associated phospholipase A(2) (Lp-PLA2) activity have been shown to be associated with increased risk of coronary heart disease and an inhibitor of this enzyme is under development for the treatment of that condition. A Val279Phe null allele in this gene, that may influence patient eligibility for treatment, is relatively common in East Asians but has not been observed in Europeans. We investigated the existence and functional effects of low frequency alleles in a Western European population by re-sequencing the exons of PLA2G7 in 2000 samples. In all, 19 non-synonymous single-nucleotide polymorphisms (nsSNPs) were found, 14 in fewer than four subjects (minor allele frequency <0.1%). Lp-PLA2 activity was significantly lower in rare nsSNP carriers compared with non-carriers (167.8±63.2 vs 204.6±41.8, P=0.01) and seven variants had enzyme activities consistent with a null allele. The cumulative frequency of these null alleles was 0.25%, so <1 in 10,000 Europeans would be expected to be homozygous, and thus not potentially benefit from treatment with an Lp-PLA2 inhibitor.
Asunto(s)
Sustitución de Aminoácidos/genética , Enfermedad Coronaria/genética , Mutación , Fosfolipasas A2/genética , 1-Alquil-2-acetilglicerofosfocolina Esterasa , Alelos , Enfermedad Coronaria/tratamiento farmacológico , Inhibidores Enzimáticos/uso terapéutico , Genética de Población , Homocigoto , Humanos , Inhibidores de Fosfolipasa A2 , Fosfolipasas A2/metabolismo , Polimorfismo de Nucleótido Simple , Análisis de Secuencia de ADN , Población Blanca/genéticaRESUMEN
Horseradish peroxidase was examined as a function of Ca and substrate binding using infrared spectroscopy in the temperature range of 10-300 K. The Ca complex could be identified by the carboxylate stretches. The amide peak positions indicate that the protein remains stable from room temperature to 10 K. Shifts in these peaks are consistent with increased hydrogen bonding as temperature decreases, but the protein conformation is maintained at cryogenic temperatures. The substrate, benzohydroxamic acid, produced no detectable change in the infrared spectrum, consistent with X-ray crystallography results. With removal of Ca, the protein maintained its overall helicity.