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Published on: February 18, 2017
Identification and purification of a liver microsomal glucose 6-phosphatase
Abstract:
1. Hepatic glucose 6-phosphatase activity was purified 65-fold in good yield over that in cholate-solubilized microsomal fractions. 2. This preparation still contained five major polypeptides and numerous minor contaminants. 3. The smallest of the five major polypeptides (Mr approx. 18 500) could be purified from heat-treated microsomal fractions. 4. Antisera raised against the heat-stable protein doublet was used to immunoprecipitate specifically glucose 6-phosphatase activity from cholate-solubilized microsomal fractions. 5. This work indicates that hepatic microsomal glucose 6-phosphatase appears to be one or both of the low-molecular-weight heat-stable polypeptides.
Insights
Researchers purified hepatic glucose 6-phosphatase, identifying it as one or both low-molecular-weight, heat-stable polypeptides. This finding advances understanding of glucose metabolism regulation in the liver.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Hepatic glucose 6-phosphatase is a key enzyme in glucose metabolism.
- Its precise molecular identity within liver microsomes has been challenging to ascertain.
- Previous studies utilized cholate-solubilized microsomal fractions for enzyme activity assays.
Purpose of the Study:
- To purify and identify the specific protein(s) responsible for hepatic microsomal glucose 6-phosphatase activity.
- To characterize the molecular properties of the enzyme.
- To develop tools for specific enzyme isolation and characterization.
Main Methods:
- Enzyme purification from cholate-solubilized microsomal fractions.
- Analysis of polypeptide composition using molecular weight markers.
- Purification of a specific low-molecular-weight polypeptide from heat-treated fractions.
- Immunoprecipitation using antisera against heat-stable protein doublets.
Main Results:
- Hepatic glucose 6-phosphatase activity was purified 65-fold with good yield.
- The purified preparation contained five major polypeptides and minor contaminants.
- A low-molecular-weight (approx. 18,500 Mr) heat-stable polypeptide was isolated.
- Specific immunoprecipitation of enzyme activity confirmed the role of heat-stable polypeptides.
Conclusions:
- Hepatic microsomal glucose 6-phosphatase activity is attributed to one or both of the identified low-molecular-weight, heat-stable polypeptides.
- This identification provides a molecular basis for understanding glucose homeostasis.
- Further characterization of these polypeptides is warranted.
