Sucrase

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Sucrase is the name given to a number of enzymes (EC 3.2.1.10, EC 3.2.1.48, EC 3.2.1.26) that catalyse the hydrolysis of sucrose to fructose and glucose. EC 3.2.1.26 is also known as invertase.

1 Physiology
2 Use in chemical analysis
3 Invertase in confectionery
4 See also
5 External links

Sucrose intolerance (also known as Congenital Sucrase-Isomaltase Deficiency (CSID) or Sucrase-isomaltase deficiency) occurs when sucrase is not secreted in the small intestine. With sucrose intolerance, the result of consuming sucrose is excess gas production and often diarrhea and malabsorption.

Sucrase is secreted by the tips of the villi of the epithelium in the small intestine. Its levels are reduced in response to villi-blunting events such as celiac sprue and the inflammation associated with the disorder. The levels increase in Pregnancy/Lactation and Diabetes as the villi hypertrophy.

Sucrose itself is a non-reducing sugar, having the reducing aldehyde group involved in the glycosidic bond, and therefore will not test positive with Benedict's solution. In order to test for sucrose, the enzyme sucrase is mixed with the sample. The sucrose is hydrolysed into glucose and fructose, with glucose being a reducing sugar, which will test positive with Benedict's solution. Fructose can be isomerized to glucose by the addition of NaOH or other strong base.

Glucose and fructose are sweeter than sucrose, dissolve in water more readily, and do not crystallize as easily; they are therefore preferred for some uses in confectionery, such as the soft centers of chocolates. Invertase (beta-fructofuranosidase, EC 3.2.1.26, E1103) is used for this purpose. For instance, a solid fondant may be prepared using sucrose and a little invertase added; after a few weeks of storage, the fondant will be partly liquefied.

For industrial use, invertase is usually derived from yeast. It is also synthesized by bees, who use it to make honey from nectar.

Invertase is expensive and when fructose is required it may be preferred to make it from glucose using glucose isomerase.

Invertase is so called because passing polarized light through a solution of an equimolar mixture of glucose and fructose (invert sugar) rotates its plane of polarization to the left, whereas doing the same with sucrose rotates the plane of polarization to the right.