RESUMEN
The phenol oxidase system is ancient and ubiquitously distributed in all living organisms. In various groups it serves for the biosynthesis of pigments and neurotransmitters (dopamine), defence reactions and tissue hardening. Ascidians belong to subphylum Tunicata, which is considered the closest living relative to Vertebrates. Two phenol oxidases previously described for ascidians are vertebrate-like and arthropod-like phenol oxidases. In our present study, we described a new ascidian protein, Tuphoxin, with putative phenol oxidase function, which bears no sequence similarity with two enzymes described previously. The closest related proteins to Tuphoxin are mollusc haemocyanins. Unlike haemocyanins, which are oxygen transporting plasma proteins, Tuphoxin is synthesised in ascidian blood cells and secreted in the extracellular matrix of the tunic-ascidian outer coverings. Single mature transcript coding for this phenol oxidase can give several protein products of different sizes. Thus limited proteolysis of the initial protein is suggested. A unique feature of Tuphoxins and their homologues among Tunicata is the presence of thrombospondin first type repeats (TSP1) domain in their sequence which is supposed to provide interaction with extracellular matrix. The finding of TSP1 in the structure of phenol oxidases is new and we consider this to be an innovation of Tunicata evolutionary lineage.
Asunto(s)
Urocordados , Animales , Células Sanguíneas , Hemocianinas/química , Monofenol Monooxigenasa/química , Fenoles , VertebradosRESUMEN
In patients who had sustained myocardial infarction including that of complicated history, the anaerobic threshold was defined to choose the optimum intensity of physical training. The latter were also examined for effects on exercise tolerance. It was ascertained that measuring physical exercise by heart rate at the level of the anaerobic threshold made it possible to choose the optimal conditions for the aerobic supply of metabolic demands during physical training. Applying physical training under aerobic conditions greatly increases exercise tolerance, prevents recurrent myocardial infarctions and plays an important role in the secondary prevention of coronary heart disease.