Trypsin activation of the red cell Ca2+-pump ATPase is calcium-sensitive.
Stimulation of the calmodulin-independent activity of the red cell Ca2+-pump ATPase by trypsin treatment (of calmodulin free red cell membranes) is sensitive to Ca2+ in a concentration range near the KCa of the transport site. The Ca2+ requirement for this effect is absolute, whereas the calmodulin sensitivity of the ATPase can be abolished by sufficient trypsin attack in the absence of Ca2+, although Ca2+ accelerates inactivation. This indicates that the two effects of trypsin are due to at least two distinct cleavage sites in the pump protein.
D001693:Biological Transport, Active / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000097:blood* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002147:Calmodulin / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000201:enzymology; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D066298:In Vitro Techniques; D014357:Trypsin / Q000494:pharmacology*
D002147:Calmodulin; D014357:Trypsin; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium