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COMMUXICATIOKS TO THE EDITOR
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for partial financial support of this work. B.B.F. gratefully acknowledges receipt of an Eastman Kodak Fellowship (1951-2) and a Signal Oil Company Mosher Fellowship (1952-3) during the tenure of which much of this work was completed.
ditions in the absence of substrate, less binding occurs and the concentrations of X and I are higher, and the exchange will proceed a t high ATP concentrations, just as has been found in \Tadkins and Lehninger’s Table I.* If, on the other hand, we assume, as Wadkins and Lehninger assume, that ( 5 ) Semiconductor Division, Hughes Aircraft Company, Culver City, California. the oxidized form of the respiratory enzyme is the high-energy carrier, we find that binding of X and DEPARTMENT O F CHEMISTRY B. B. FISHER& OF CALIFORNIA I as X I and b. * -1 is maximal under aerobic UNIVERSITY Los ANCELES, CALIF. W. G. MCMILLAN conditions and minimal under anaerobic conditions. RECEIVED APRIL 24, 1957 This leads to the conclusion that the exchange reaction should have gone more rapidly under anSITES O F ENERGY CONSERVATION IN OXIDATIVE aerobic conditions than under aerobic conditions which i t did not do. PHOSPHORYLATION I t now may be concluded that \i,Tadkiiisand Leh Sir: ninger’s data on the 10-fold acceleration of the Direct spectroscopic and kinetic studies of re- ATP-Pi3’ exchange reaction under aerobic condispiratory carriers in mitochondria have led to the tions support our earlier conclusions: (a) that the conclusion that the reduced forms of the carriers, reduced forms of the respiratory pigments repreespecially DPNH, are involved in the “high en- sent the carriers of the “high-energy” complex ergy” complexes which are intermediates in the and (b) that intermediates exist between the rephosphorylation of ADP.‘ Wadkins and Lehn- spiratory carriers and ADP. inger reached the opposite conclusion on the basis of The ATP-Pi32 exchange reaction is a t present an experiment on the effect of aerobiosis and an- poorly understood and may not yet provide a subaerobiosis on the ATP-Pi32 exchange reaction.2 stantial basis for proof of any further hypothesis; We show here that their interpretation of their ex- the reaction is slow in the digitonin preparation, perimental result is not unique and actually affords requires high ATP concentrations, and is affected support for the conclusion they seek to refute. by added ADP a t concentrations outside the range The reaction mechanism for oxidative phos- of that needed for maximal rate of electron transphorylation on which Wadkins and Lehninger fer.’ However, Wadkins and Lehninger’s dat‘t based their conclusions ignores spectroscopic stud- appear to provide additional evidence th:rt thc ies of the rate with which ADP and uncoupling “high-energy” complex involves the reduced caragents interact with the respiratory carriers.” rier. In their Table I, they find that the incorSuch studies indicate that two intermediates inter- poration of into ADP to form ATP32gives vene between ADP and the carriers, More re- over 67 times as much incorporation when the cently, Myers and Slater, in a study of ATP-ase carriers are reduced than when they are oxidixd. activity of mitochondria, have concluded that Since the mitochondria are stated to be anaerobic. their results support the existence of such inter- this phosphorylation is attributed to the presence m e d i a t e ~ . ~Cohn and Drysdale have also pro- of the “high-energy” complexes of the reduced carposed multiple intermediates in the phosphorus riers. and oxygen exchange reactions.6 One formulation Thus the data of IVadkins and Lehningcr sui)for the function of two such intermediates in the port in two ways our conclusion’ that the reduced oxidative phosphorylation mechanism for a partic- form of the respiratory carrier serves as the site of ular pair of respiratory catalysts has been repre- the “high-energy” complex. The transition froin sented’ oxidized to reduced carriers gives first a one-tenth 1 1 “ ’ +- I -++b ” ’ . I (1) as rapid catalysis of the ATP-Pi3’ exchange reaction caused by a binding of the reaction inter),“‘.1 +c”+c”‘+h“NI (2) mediates X and I by the reduced carriers ami. 1)’ I + x +b’ + x I (3) second, a 6?-fold greater anaerobic phosphorylas - I + P c-2-x P + I (4) tion of ADP caused by “high energy” compounds S -P ADP-++ ATP -j- X (5) of the reduced carriers. ‘Ihc A r P - P X 2exchange reaction is presumed to in(7) C. Cooper and A. I.. Lchninger, ibid., 224, 561 (1937). volve the reversible reactions of X and I in Eq. 4 JOHNSON RESEARCH FOUWJATIOS and 5, and not the respiratory carriers directly, UNIVERSITY OF PENNSYLVANIA BRITTOSC I ~ A S C I C MEDICAL SCHOOL GUNNAR HOLLUNGER as Wadkins and Lehninger propose. The amounts 4, PESNSYLVANIA of X and I available depend indirectly upon PHILADELPHIA RECEIVED MARCH20, 1957 aerobiosis and anaerobiosis. Under anaerobic con___ ditions X and I can be bound as X I and b” I, and the exchange will be slow. Under aerobic conTHE CONVERSION OF myo-INOSITOL TO
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(2) C . I>, Wai!kini and A . I.. I~+hninger,’ r H I S JOURNAL, 79. 1010 (1957). (3) 13. Chance arid G. K. William:?. J Erol C h c m . , 221. 477 (195Gj. ( % ) 1). I
