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Salivary amylase and other enzymes in saliva

When food enters the mouth it triggers the release of saliva. Saliva contains enzymes that have important biological functions. Like other enzymes in the body, salivary enzymes help catalyze or speed up the rate of chemical reactions in the body. The action of enzymes in saliva is necessary for the development of digestion, an essential process for the incorporation of energy and nutrients from the food we eat. It can be said that insalivation is the first chemical activity of digestion.

The main enzymes in saliva

  • Salivary amylase  (also known as ptyalin) breaks down starches into sugars, smaller molecules.
  • Salivary kallikrein  helps produce bradykinin, a blood vessel dilator and regulator of blood pressure.
  • Tongue lipase  helps break down triglycerides (fats) into fatty acids and glycerides.

salivary amylase

Salivary amylase is the main enzyme in saliva. Salivary amylase breaks down carbohydrates into smaller molecules, sugars. The breakdown of macromolecules into simpler molecules is part of the food digestion process; in the case of salivary amylase, it acts specifically in the first stage of the degradation of the starch present in potatoes, rice or pasta.

During this process, large carbohydrate molecules such as amylopectin and amylose are converted to maltose. Maltose is a sugar that is made up of glucose subunits, the main source of energy in the human body. 

Salivary amylase also has a function associated with dental health: it helps prevent starches from accumulating on the teeth. In addition to salivary amylase, humans also produce pancreatic amylase, which continues the breakdown of starches later in the digestive process.

Salivary kallikrein

Kallikreins are a group of enzymes that participate in the breakdown of high molecular weight compounds, such as kininogen, and break them down into smaller molecules. Salivary kallikrein breaks down kininogen into bradykinin, a vasodilator. Bradykinin helps control blood pressure: it causes blood vessels to dilate, causing blood pressure to drop. Saliva only contains small amounts of kallikrein.

lingual lipase

Lingual lipase is an enzyme that breaks down triglycerides into glycerides and fatty acids, thus catalyzing lipid digestion. This process begins in the mouth, where triglycerides are broken down into diglycerides. Unlike salivary amylase, which acts in non-acidic environments, lingual lipase can act in an acidic pH environment, so its action continues and becomes more intense in the stomach.

Lingual lipase helps babies digest the fats in breast milk. With growth, the proportion of tongue lipase in saliva decreases as other parts of the digestive system have a greater role in digesting fats.

Other salivary enzymes

Saliva contains other enzymes such as salivary acid phosphatase, which releases phosphoryl groups from other molecules that make up food. Like amylase, acid phosphatase aids in the digestion process.

Saliva also contains lysozymes, enzymes that help kill bacteria, viruses, and other pathogenic organisms; these enzymes have antimicrobial functions.

Sources

  • Becker, Andrea. Names of the Enzymes in the Mouth & Esophagus.  Sciencing.com, Sciencing, 10 Jan. 2019, sciencing.com/names-enzymes-mouth-esophagus-17242.html.
  • Marie, Joanne. What Are the Functions of Amylase, Protease and Lipase Digestive Enzymes . Healthy Eating SF Gate, 12 Dec. 2018, healthyeating.sfgate.com/functions-amylase-protease-lipase-digestive-enzymes-3325.html.