Cardiac sarcoplasmic reticulum Ca2+ pump as a target for benzoquinones.
1. Three benzoquinones (p-benzoquinone, 2,5-dimethyl-p-benzoquinone and tetramethyl-1,4-benzoquinone), differing for their electrophilicity, were tested on Ca2+ ATPase activity of cardiac sarcoplasmic reticulum membrane vesicles. 2. Only p-benzoquinone and 2,5-dimethyl-p-benzoquinone inhibited Ca2+ ATPase activity in a time-and concentration-dependent way, tetramethyl-1,4-benzoquinone being ineffective. 3. p-Benzoquinone and 2,5-dimethyl-p-benzoquinone decreased in a concentration-dependent way the total--SH groups of cardiac sarcoplasmic reticulum vesicles. 4. The results suggest that the most electrophilic benzoquinones interact directly with some critical--SH groups of Ca2+ pump inhibiting the enzymatic activity.
Floreani
M
M
Department of Pharmacology, University of Padova, Italy.
Forlin
A
A
Bellin
S
S
Carpenedo
F
F
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002417:Cattle; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology* / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology
D016227:Benzoquinones; D002132:Calcium Radioisotopes; D009124:Muscle Proteins; D013438:Sulfhydryl Compounds; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium