Rennin (Enzyme)

Enzymes are bio-catalytic substances that are produced by our bodies. Enzymes are associated with various functions of the body such as digestion, metabolism, growth, development etc. Rennin (a.k.a chymosin) is an enzyme which belongs to class protease. Rennin and pepsin are the only two enzymes produced in the stomach. Rennin is produced immediately after birth by the stomachs of young mammals in its inactive form. In human babies, rennin is primarily associated with coagulation of milk. This property of rennin is very much useful for digestion of milk in babies.

How is Rennin Produced

Rennin is present in the human body in the form of an inactive agent called prorennin. When you consume milk, hydrochloric acid is immediately formed in the stomach. Hydrochloric acid activates the inert prorennin and signals it to produce rennin. Milk comprises protein caseinogen, which is made up of four different types of molecules alpha-s1, alpha-s2, beta-casein and kappa-casein. Out of these four molecules, first three types of molecules can precipitate milk in the presence of calcium. However, the fourth molecule kappa-casein, does not precipitate milk. Further, it inhibits the precipitation of the other three molecules. Rennin, which is active enzyme in rennet masks kappa-casein, so that other three molecules are precipitated.

Importance of Rennin in Human Body

As mentioned before, rennin is present in the inactive state prorennin at the time of birth. Rennin is primarily associated with curdling of milk. The digestive systems of young ones are not developed. Hence, there is a chance that the milk may flow out of the body, without any absorption of nutrients. If this happens, the baby will be deprived of the vital nutrients in milk, which may affect her growth. To prevent this, it is necessary that the milk should stay in the body for a longer time. This is possible only when the milk is in the curdled form. This function is carried out by rennin. Interestingly, the conversion of milk into curd is possible only at 37 degree Celsius, which is the temperature of human body.

Applications of Rennin

The production of rennin in the human body begins to diminish as one grows old. Rennin is then replaced by pepsin, which is another digestive enzyme produced by the stomach. Applications of rennin in food industry are widely known. Rennin is used for coagulating milk to form various milk products such as cheese. Earlier, the rennin used for this purpose was obtained from the dried stomachs of young calves. However, the quantity of rennin obtained thus, was limited, hence not sufficient for the industrial demand. Since then, rennin required for food industry is genetically processed. Rennin is also found in certain plant sources like nettles and thistles and also in microorganisms like yeast and fungi.

Laboratory experiments have proved that rennin can only function at an optimum temperature of 37 degree Celsius. At higher temperatures, the molecular activity is increased due to increase in energy. This leads to disintegration of chemical bonds in rennin, which affects the active site of enzyme. Due to the change in active site, the substrate molecule (milk molecule) cannot fit in the active site. Thus precipitation fails. At lower temperatures, the molecular activity decreases, slowing down the rate of reaction. At 0 degree Celsius, the reaction stops entirely.

Thus, rennin enzymes play a vital role in the nutrition of young mammals. Rennin is sometimes also mistaken with renin, an enzyme secreted by kidneys, which has entirely different functions. Thus, rennin and renin are different, hence the two terms should not be used interchangeably.