Adp regenerating enzyme systems in mitochondria of the guinea pig
myometrium and heart.
Clark, Joseph F., Andrey V. Kuznetsov, and George K. Radda.
Department of Biochemistry, University of Oxford, South Parks Road,
Oxford OX1 3QU, England
APStracts 3:0289C, 1996.
Any enzyme or enzyme system that produces ADP in proximity to the
mitochondria may be capable of stimulating respiration. Hexokinase
(HK), Adenylate kinase (AK), and mitochondrial creatine kinase (Mi
-CK) all catalyse reactions that produce ADP and thus may play a role
in cellular nucleotide metabolism or control of mitochondrial
oxidative phosphorylation. Respiratory characteristics and enzyme
activities of mitochondria simultaneously isolated from heart and
uterus of the gravid guinea pig, were compared. The ability of AMP,
glucose, and creatine to stimulate mitochondrial respiration via AK,
HK, and Mi-CK systems respectively was examined. Though the uterine
Mi-CK activity is low compared to the values found in heart, the
activities of HK and AK were significantly greater. Furthermore, the
ability of HK and AK to stimulate respiration (functional activity),
was greater in the uterine mitochondria. Indeed the activity of AK
was sufficient to generate maximal (State 3) respiration. The
apparent Km for ADP to stimulate respiration in the isolated uterine
mitochondria was significantly different from that of the heart (9.6
+/- 0.9 and 5.1 +/- 1 [mu]M ADP respectively). It is concluded that
uterine mitochondria can use HK and AK systems in addition to the CK
system in enhancing local ADP concentration which may aid in the
mitochondrial responses to energetic demands.
Received 21 March 1995; accepted in final form 28 August 1996.
APS Manuscript Number C157-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996