Hydrolysis reactions
DNA decay by hydrolysis can occur abiotically and be enzymatically
mediated and is affected by environmental factors (e.g., water pH,
temperature, and ionic strength). DNA strands break through enzymatic
hydrolysis by so-called DNases. Such DNA enzymatic hydrolysis can occur
at high rates and become the main driver of DNA decay as opposed to
purely abiotic
hydrolysis3,15.
Determining how environmental parameters change enzymatic hydrolysis
rates is complicated by the fact that each species’ enzymes potentially
exhibit optimal kinetics for different possible combinations of
environmental parameters because of a species’ evolutionary history of
adaptation43.
Abiotic hydrolysis reactions, such as depurination (loss of purine base)
and deamination of cytosine (elimination of ammonia), followed by strand
break cause DNA decay. Chemical depurination rates decrease with
decreasing temperature, pH, and ionic strength. Deamination reactions
are very slow at temperatures present for most of earth’s surface waters
(excluding hydrothermal vents) and are therefore unlikely to be an
important driver of DNA decay on short time scales of days to
weeks44.
In fact, most estimates of abiotically driven hydrolysis (depurination
and deamination) of DNA have half-lives between 70 and 31,000,000 years,
but these can be modulated by extreme environmental
conditions3.