Question

Briefly explain how the enzyme urease is utilized by certain bacteria.

Answer 1

Urea is a small molecule formed as proteins are broken down.It is excreted in urine,but it is not particularly toxic at low levels so it is found in the cells throughout the body.As urea contains Nitrogen (N) several pathogens have adopted to use it as a nitrogen source using an enzyme called urease to break it down.

The urease converts urea into ammonia and carbamic acid,which then spontaneously reacts with water to form carbonic acid(and produces another ammonia).Converting the carbonic acid into bicarbonate produces a buffer solution:the ammonia and bicarbonate can bond with and dissociate from free hydrogen ion enough to keep the pH of the surrounding area relatively neutral.This is particularly useful for bacteria such as Helicobacter pylori which colonises the stomach and therefore needs to cope with very acidic conditions.

Urease is also very important for bacteria that infect the urinary tract such as the Proteus and Klebsiella species.In these bacteria,the carbonic acid and ammnia can bind with minerals such as magnesium and calcium to form "infectious stones"-hard coatings that surround and protect the bacteria.