Salivary Amylase and Other Enzymes in Saliva

Saliva
Saliva contains a number of enzymes.

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When food enters the mouth, it triggers the release of saliva. Saliva contains enzymes that perform important biological functions. Just like other enzymes in the body, the salivary enzymes help to catalyze, or speed up, the rate of chemical reactions in the body. This function is required to promote digestion and the acquisition of energy from food.

Major Enzymes in Saliva

  • Salivary amylase (also known as ptyalin) breaks down starches into smaller, simpler sugars.
  • Salivary kallikrein helps produce a vasodilator to dilate blood vessels.
  • Lingual lipase helps to break down triglycerides into fatty acids and glycerides.

Salivary Amylase

Salivary amylase is the primary enzyme in saliva. Salivary amylase breaks down carbohydrates into smaller molecules, like sugars. Breaking down the large macromolecules into simpler components helps the body to digest starchy foods, like potatoes, rice, or pasta.

During this process, larger carbohydrates, called amylopectin and amylose, are broken down into maltose. Maltose is a sugar that is composed of individual subunits of glucose, the human body's key source of energy. 

Salivary amylase also has a function in our dental health. It helps to prevent starches from accumulating on our teeth. In addition to salivary amylase, humans also produce pancreatic amylase, which further breaks down starches later in the digestive process.

Salivary Kallikrein

As a group, kallikreins are enzymes that take high molecular weight (HMW) compounds, like kininogen, and cleave them to smaller units. Salivary kallikrein breaks down kininogen into bradykinin, a vasodilator. Bradykinin helps to control blood pressure in the body. It causes blood vessels to dilate or expand and causes blood pressure to be lowered. Typically, only trace amounts of salivary kallikrein are found in saliva.

Lingual Lipase

Lingual lipase is an enzyme that breaks down triglycerides into glycerides and fatty acid components, thus catalyzing the digestion of lipids. The process begins in the mouth where it breaks down the triglycerides into diglycerides. Unlike salivary amylase, which functions best in non-acidic environments, lingual lipase can operate at lower pH values, so its action continues into the stomach.

Lingual lipase helps infants digest the fats in their mother's milk. As we get older, the relative proportion of lingual lipase in saliva decreases as other parts of our digestive system help with fat digestion.

Other Minor Salivary Enzymes

Saliva contains other minor enzymes, like salivary acid phosphatase, which frees up attached phosphoryl groups from other molecules. Like amylase, it helps with the digestion process.

Saliva also contains lysozymes. Lysozymes are enzymes that help to kill bacteria, viruses and other foreign agents in the body. These enzymes thus perform 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.