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Biomedical subjects

B Wallmark

Publications and source records attributed to B Wallmark.

60 records · Page 4Linked to original sources
PubMed1980

The interaction of K+ with gastric parietal cells and gastric ATPase.

The gastric H+ secretion in isolated cell requires K+ and is ATP dependent. There is also evidence in the cell system for Na+ inhibition of H+ secretion. The isolated gastric ATPase also shows K+ activation and inhibition by K+ or Na+ located on the ATP binding side of the enzyme, which corresponds to the cytoplasmic face of the enzyme. Gastric vesicles are activated in terms of transport activity by internal K+, and this site, inhibited by reagents that modify carboxyl groups, is required for enzyme turnover and transport.

Adenosine Triphosphate↗
PubMed1980

Aspects of parietal cell biology: cells and vesicles.

Many features of these gastric vesicles satisfy the requirements for the gastric H+ pump. For example, we have: (a) K+ requirement, (b) KA for K+ of about 30 mM; (c) identical cation sequence for tissue and vesicles, (d) similar anion sequence, (e) localization at the microvillus of the secretory canaliculus, (f) TI+ inhibiting H+ transport of both systems, and (g) the K+ gradient satisfying the osmotic gradient requirement for HCl-flow out of the parietal cell. Points that require explanation are lack of SCN- effects and regulation of KCl permeability.

Adenosine Triphosphatases↗
PubMed1979

Phosphorylation and dephosphorylation kinetics of potassium-stimulated ATP phosphohydrolase from hog gastric mucosa.

Partial reactions of potassium-stimulated ATP phosphohydrolase from hog gastric mucosa were studied by means of a rapid-mixing apparatus. At 21 degrees C, in the presence of 2 mM MgCl2 and 5 microM [gamma-32P]ATP there was a rapid phosphorylation of the enzyme with a pseudofirst order rate constant of 1400 min-1. Addition of the ATP about 120 ms before the MgCl2 increased this rate constant to 4400 min-1. In the absence of MgCl2 there was no phosphorylation. Addition of 4 or 10 mM KCl to the phosphoenzyme which had been formed in the absence of KCl produced a rapid initial rate of dephosphorylation (k = 2600 and 3200 min-1 respectively). An additional slow component of dephosphorylation was observed when unlabeled ATP was added together with the KCl (k = 700 to 900 min-1). At a 4 mM concentration, KCl stimulated the ATPase activity about 9-fold. At higher concentrations, the activity was reduced in parallel with a reduction of the steady state level of phosphoenzyme. Addition of KCl to the enzyme before the addition of ATP plus MgCl2 resulted in a low rate and extent of phosphorylation. KCl appeared to inhibit the phosphorylation at a level preceeding the E.ATP complex.

Adenosine Triphosphatases↗