Volume changes during enzyme reactions: indications of enzyme pulsation during fumarase catalysis.

Overall activation volumes for multistep reactions are not usually pressure independent. The present investigation gives a quantitative description of this effect under Theory. Simple relations are obtained which can easily be applied to experimental data and which allow more insight into the dynamics of enzyme reactions. This is demonstrated under Experimental Application for the conversion of fumarate to L-malate catalyzed by the enzyme fumarase. The volume profile of this reaction indicates a pulsation of the enzyme molecule during catalysis. The appendix discusses the question whether Eyring's transition-state theory is an appropriate basis for investigations of this kind.