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Measuring Lactase Enzymatic Activity in the Teaching Lab
04:41

Measuring Lactase Enzymatic Activity in the Teaching Lab

Published on: August 6, 2018

The nature of small bowel luminal fluid lactase

S H Quak1, G A Brown, I W Booth

  • 1Department of Paediatrics, National University Hospital, Singapore.

Clinica Chimica Acta; International Journal of Clinical Chemistry
|December 31, 1991
PubMed

Insights

Jejunal fluid lactase activity in children originates from the microvillous membrane of enterocytes. This study confirms that lysosomal acid lactase does not significantly contribute to jejunal fluid lactase levels.

Area of Science:

  • Gastroenterology
  • Pediatric Gastroenterology
  • Enzymology

Background:

  • The source of jejunal fluid lactase activity in children remains unclear.
  • Understanding lactase origin is crucial for diagnosing and managing lactose intolerance.

Purpose of the Study:

  • To investigate the mucosal origin of jejunal fluid lactase activity in children.
  • To differentiate the contribution of microvillous membrane lactase versus lysosomal acid lactase.

Main Methods:

  • Simultaneous collection of jejunal mucosa and fluid from 15 children.
  • Measurement of lactase activity in mucosal homogenates, enterocyte microvillous membrane fractions, and jejunal fluid.
  • Kinetic and pH optima studies, including assessment with a lysosomal acid lactase inhibitor.

Main Results:

  • Jejunal fluid lactase activity strongly correlated with microvillous membrane fraction activity (r=0.889) and mucosal homogenate activity (r=0.807).
  • Kinetic and pH optima supported a microvillous membrane origin for the fluid enzyme.
  • Lysosomal acid lactase inhibition did not alter jejunal fluid lactase activity or pH optimum.

Conclusions:

  • Jejunal fluid lactase activity in children primarily reflects the activity of the microvillous membrane enzyme.
  • Lysosomal acid lactase does not measurably contribute to the total lactase activity found in jejunal fluid.

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