In the context of the Hill coefficient, the Akt tumor kinetic behaviour was defined as cooperative (or positively cooperative in contexts where ambiguity might otherwise be likely) for h>1, negatively cooperative for h<1, and non-cooperative for h=1. This section introduced the terms free enzyme, enzyme–substrate complex, enzyme–product complex, enzyme–inhibitor complex, etc., all of them in an obvious way that does not require discussion. Complexes between two entities were defined as binary complexes, and higher-order complexes as ternary complexes and quaternary complexes. The term substituted enzyme was suggested

for a second form of free enzyme differing from the first by the presence of a covalently bound group that is transferred in the reaction. The panel seems to have avoided the question of whether such a mechanism should be called a substituted-enzyme mechanism or a ping pong mechanism, as neither name was mentioned. Other terms defined essentially as one would find in a textbook were dead-end complex, dead-end reaction, abortive complex, and non-productive complex, compulsory-order mechanism, random-order Inhibitor Library mw mechanism,

branched mechanism, preferred-order mechanism, binding step, release step, isomerization and allosteric effector. Mechanisms as the term would be understood by an organic chemist were not considered. The catalytic activity of an enzyme was defined as the property measured by the increase in the rate of conversion (i.e. the

rate of reaction multiplied by the volume: see above) of a specified chemical reaction learn more that the enzyme produces in a specified assay system. Note that this is an extensive quantity, because it needs to increase with the total amount of enzyme activity. Derived quantities are the specific catalytic activity, the catalytic activity divided by the mass of protein, and the molar catalytic activity, the catalytic activity divided by the number of moles of enzyme catalytic centres or of multi-centre molecules. This consisted mainly of a Table of symbols and units, with no important information not already dealt with. In most respects the earlier sections of the original recommendations, and also the discussion of enzyme activity at the end, have survived well, and that although some revision might be desirable this could easily be done by a new Commission set up by the IUBMB. The later sections are another matter, however. It is not obvious that there is a very strong demand for new recommendations on activation terminology, but this could likewise be done without great difficulty by a Commission of experts in this field.