Fever doesn’t kill bacteria or enzymes:
Usefulness
There are arguments for and against the usefulness of fever, and the issue is controversial.[22][23] There are studies using warm-blooded vertebrates[24] and humans[25] in vivo, with some suggesting that they recover more rapidly from infections or critical illness due to fever. A Finnish study suggested reduced mortality in bacterial infections when fever was present.[26]
In theory, fever can aid in host defense.[22] There are certainly some important immunological reactions that are sped up by temperature, and some pathogens with strict temperature preferences could be hindered.[27]
Research[28] has demonstrated that fever assists the healing process in several important ways:
Increased mobility of leukocytes
Enhanced leukocyte phagocytosis
Endotoxin effects decreased
Increased proliferation of T cells[29]
40° C (104° F) is given as the approximate maximum temperature at which living processes can safely and faultlessly operate.
It’s not only a matter of destruction of organic molecules (enzymes being only one of several kinds), but above all, of the generation of abnormal chemical compounds such as Maillard’s molecules / AGEs.
If you put you food in an oven at 77° C (170° F), thousand billions of innumerable various Maillard’s molecules / AGEs will form at the surface, even if the inside remains at 37° C (99° F).