The current rapid loss of species is considered by many scientists to be another mass extinction. what may be causing this increase in extinction rate, beyond background extinction?

There have been 5 mass extinctions in the history of Earth, the main two are the K-T extinction (75% of the world organisms were killed) and the great paleozoic extinction. Scientists believe a massive meteorite caused the KT extinction but could also have been caused by some traps in India. The paleozoic extinction was believed to be caused by traps in Siberia which effected the temperature and atmospheric conditions of the tune

enzymes loose their form in both unsuitable ph and temprature.

Explanation:

at very high tempratures enzyme molecules denatures due to high speed movements, at low tempratures enzymes works too slow to be useful enough.

low ph solotions contain lot of H+  and high ph solutions have few H+ , and the number of these H+ ions have polar effects on enzymes.  some Enzymes like pepsin works perfect in acidic environment ( ph=2)  while others might work at  high ph  or average ph( like Trypsin  works well at ph=7).