Protein coagulation and essential life-denaturation are completely different things. The second has already preceded the first, but the second not necessarily gives rise to the first. Some researchers describe the, by us not discussed, native-denaturation --- [a "native" protein is a protein extracted from a living organism] (we here discuss the vital-denaturation [i.e. the denaturation of a truly living protein, as it is still in the living body, studying it not as a process, but as a state] ) --- as to be an "unwinding" (unfolding) of protein. This would match with the view of the cancellation of a fixed special configuration. Strike-theoretically one thinks of the S-S and H-bridge separation [respectively the break of a sulphur-sulphur bond and of the hydrogen bond]. It is also surmised that in the initially reversible, and later irreversible protein denaturing as a result of heat, it is about a chain reaction [i.e. a reaction between chains] between intra-molecular S-S of a molecule and SH-groups of a second molecule, in which an inter-molecular S-S is formed (only making sense in the system-view of orgasnisms if one has certain molecules in mind that are permanent also when they in reality have disappeared as a result of new chemical bonds [In Unimol we do not speak of individual separate molecules, but of typical parts of the one living molecule, parts which we may happily call "proteins", or even "protein molecules".] ).
As to denaturation, there is a marked poly-aetiology [meaning that there are many causes of denaturation]. In many respects it is similar to a melting event. It is endothermic [meaning that it, in order to take place, takes up energy from the environment], but is nevertheless spontaneous at lower temperatures, for the "driving force" in denaturation is the strong increase of entropy [= heat, not able to perform work] in the process of rearranging [and increase of entropy is always spontaneous]. The activation energy is high in denaturation because a substantial number of H-bridges has to be broken. On the other hand, one believes that denaturation -- reducible to an extensive scattering of the weak bonding system between the amino-acid side-chains -- doesn't need the breaking up of a large number of hydrogen bonds within the polypeptid helix, so that the protein molecule essentially is preserved as to its configuration.
In denaturation one also speaks of "unfolding", and meaning with it a rearrangement of figuration. A series of physical changes appearing in denaturation are not unconditionally characteristic, for they may be restored by some "follow-up treatment", without, however, the other lost properties such as biological activity, serological specifity, and others, reappearing again. A far-reaching "renaturation" succeeds in certain crystallizable (!) proteins such as hemoglobine, serumalbumine, trypsine, etc., but also here irreversible changes have remained, recognizable by the fact that they may more easily be split up by enzymes, have higher chemical sensitivity, etc. Renaturation, reversible denaturation in the usual sense, is, as to vital-substance, certainly totally out of the question. Both kinds of denaturation, respectively the substrates native protein and vital protein, should always be distinguished from each other. [Denatured native protein may be renatured again, resulting in renatured native protein. Denatured vital protein, on the other hand, cannot be renatured into vital protein.]
The estimated heat intensity [heat release] in the process of denaturation of 70-130 000 cal/mole has in itself the magnitude of [that of] a chemical bond. However, it must contain some amount of "crystallization"-energy or energy-of-rearrangement. One cannot conclude much from it [i.e. from the heat involved in denaturation], because it here always concerns an ultimate difference-amount constituted from whatever exothermic and endothermic rearrangements. It means that one cannot judge the difference between native [in contrast to vital] and denatured protein in this way.
One should also note that a denaturation can often already be achieved by relatively mild interventions such as shaking. Concerning the true living [state], one may say that "outside" [seen from the living], denaturation always takes place -- already the mildest intervention of contact with the outside therefore suffices -- which then also attacks the inside when the latter is increasingly changed into the outside by injurious interventions. [That is to say that wherever truly living substance is in direct contact with the inorganic outside world, denaturation phenomena set in.]