[lak-teys, -teyz]
noun Biochemistry.
an enzyme capable of hydrolyzing lactose into glucose and galactose.

1890–95; lact- + -ase Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
lactase (ˈlækteɪs, -teɪz)
any of a group of enzymes that hydrolyse lactose to glucose and galactose
[C20: from lacto- + -ase]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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American Heritage
Medical Dictionary

lactase lac·tase (lāk'tās')
See beta-galactosidase.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
lactase   (lāk'tās')  Pronunciation Key 
An enzyme that is found in the small intestine, liver, and kidneys of mammals and catalyzes the breakdown of lactose into galactose and glucose.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


any of a group of enzymes found in the small intestine, liver, and kidney of mammals that catalyze the breakdown of lactose (milk sugar) into the simple sugars glucose and galactose. Lactase is particularly abundant during infancy. The enzyme is thought to be produced by the mucous membrane cells that line the intestinal walls; granules localize in the brush border (a chemical barrier through which food must pass to be absorbed) that coats the intestinal villi.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Lactose intolerance happens when the small intestine does not make enough of the enzyme lactase.
They will need to be given supplements with the enzyme lactase so that they can tolerate milk products.
Babies always made lactase, the enzyme that breaks down this sugar, but after weaning lactase production would stop.
Lactase enzyme preparations are used to reduce the lactose content of milk and milk-derived food products.
Image for Lactase
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