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Differences between duodenal and jejunal rat alkaline phosphatase
C Calhau1, F Martel, C Hipólito-Reis
1Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal. ccalhau@med.up.pt
Clinical Biochemistry
|December 22, 2000
Summary
Rat tissue-nonspecific-alkaline phosphatase (TNS-ALP) and intestinal alkaline phosphatases (IALP) show distinct kinetic properties and drug sensitivities. Duodenal and jejunal IALP likely have different physiological roles in dephosphorylation.
Area of Science:
- Biochemistry
- Enzymology
- Physiology
Background:
- Alkaline phosphatases (ALPs) are crucial enzymes involved in phosphorylation and dephosphorylation processes.
- Tissue-nonspecific-alkaline phosphatase (TNS-ALP) and intestinal alkaline phosphatases (IALPs) are distinct isoforms with potentially different functions.
Purpose of the Study:
- To kinetically characterize rat TNS-ALP and IALPs from the duodenum and jejunum.
- To investigate the effects of specific compounds on TNS- and IALP activity.
Main Methods:
- Enzyme kinetic characterization of rat TNS-ALP and IALPs.
- Assay of ALP activity in the presence of levamisole and octreotide.
- Reverse transcription-polymerase chain reaction (RT-PCR) for IALP mRNA detection.
Main Results:
- ALP activity ranking: duodenal IALP > jejunal IALP > kidney TNS-ALP > brain TNS-ALP.
- Levamisole inhibited kidney/brain TNS-ALP but affected jejunal IALP differently than duodenal IALP.
- Octreotide increased ALP activity in brain and jejunum, with a biphasic effect in the duodenum.
- IALP-I mRNA found in both duodenal and jejunal mucosa; IALP-II mRNA only in duodenal mucosa.
Conclusions:
- Duodenal and jejunal IALPs exhibit distinct kinetic parameters and drug sensitivities.
- These differences suggest unique physiological roles for duodenal and jejunal IALPs in dephosphorylation processes.