The effects of putrescene, spermidine and spermine on membrane-bound acetylcholinesterase from human erythrocyte ;ghosts' and the solubilized enzyme of the electric organ of the electric eel were studied by kinetic methods. Measurements were made by using a photometric method which made it possible to record the enzyme reaction in the steady-state phase. Substrate-concentration-dependent activation and inhibition of acetylcholinesterase by polyamines is similar to that by Na(+), K(+), Ca(2+), Mg(2+) and certain quaternary and bisquaternary amines. The kinetics suggest an allosteric reaction mechanism. On the basis of the kinetic results a role for the polyamines as modulators of synaptic acetylcholinesterase is proposed.
The influence of various peptides containing the aromatic amino acids phenylalanine and tyrosine on the formation of the enzyme EAC1423 of the complement system from component C3 and enzyme EAC142 was investigated.
The Cobra venom factor (VF) is able to form a complex with Factor B of the alternative pathway of the complement system, which then in the presence of Factor D or trypsin is activated to the C3 cleaving enzyme VF-B̄. C3 activation caused by the enzyme in serum is accompanied by an activation of the components C5 to C9. The reaction mechanism which controls the activation of C5 has been unclear until now. We have generated the VF-B̄ enzyme in three different ways; I, with VF in serum followed by purification of the enzyme; II, with VF, B and D and subsequent Sephadex G-200 gelfiltration; and III, with VF, B and trypsin and subsequent Sephadex G-200 gelfiltration.
The activity of these three enzymes was tested against purified guinea pig C3, C5, and a mixture of C3 and C5. The following observations were made: All three enzymes induce fast C3 activation with accumulation of C3b and C3a; C3b is detected afterward on the enzymes antigenically, on enzyme I immediately after the generation and purification procedure.
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