The effect of physiological concentrations of caffeine (purified from Persian tea) on adenosine deaminase (ADA) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mM Tris-HCl buffer (pH 7.3) at 37°C was investigated, using UV-VIS spectroscopy. ADA exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine...

besides being a metabolite of nucleotides like atp, adenosine is a mediator of neuronal function in the central nervous system. its actions are mediated by at least three extracellular receptors. in this review different aspects of adenosine such as biosynthesis, release, inactivation and its receptors are discussed. it also covers pre- and postsynaptic effects as well as postreceptor mechanism...

An inherited deficiency of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is associated with an autosomal recessive form of severe combined immunodeficiency disease. Affected patients exhibit markedly reduced or absent adenosine deaminating activity in various tissues. In this study we have demonstrated the presence of a low level aminohydrolase activity in 11 different normal and a...

It is well established that in the CNS, endogenous adenosine plays a pivotal role in neurodegeneration. A low, nanomolar concentration of adenosine is normally present in the extracellular fluid, but it increases dramatically during enhanced nerve activity, hypoxia or ischemia. In these pathological conditions, adenosinergic transmission-potentiating agents, which elevate adenosine level by eit...

The adenosine kinase enzymes from arabinofuranosyladenine-resistant (araAr) mutants of the baby hamster kidney cell line were analyzed using adenosine kinase-specific antibody probes purified by adenosine kinase-Sepharose column chromatography. Wild-type baby hamster kidney cells were shown to produce two adenosine kinase polypeptides of Mr 43,000 and 40,000. The class I araAr mutants that have...

In asthmatic patients, airway obstruction provoked by exercise challenge is accompanied by an increase in plasma adenosine level. In this study, the current authors investigated if exercise-induced bronchoconstriction was associated with local changes of adenosine concentration in the airways. Oral exhaled breath condensate (EBC) collection (5-min duration) and forced expiratory volume in one s...