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. 2009 Aug 15;488(2):100-4.
doi: 10.1016/j.abb.2009.07.004.

Mitochondrial malic enzyme (ME2) in pancreatic islets of the human, rat and mouse and clonal insulinoma cells

Michael J MacDonald  1 , Melissa J Longacre, Mindy A Kendrick
Affiliations

Mitochondrial malic enzyme (ME2) in pancreatic islets of the human, rat and mouse and clonal insulinoma cells

Michael J MacDonald et al. Arch Biochem Biophys. .

Abstract

Despite interest in malic enzyme(ME)s in insulin cells, mitochondrial malic enzyme (ME2) has only been studied with estimates of mRNA or with mRNA knockdown. Because an mRNA's level does not necessarily reflect the level of its cognate enzyme, we designed a simple spectrophotometric enzyme assay to measure ME2 activity of insulin cells by utilizing the distinct kinetic properties of ME2. Mitochondrial ME2 uses either NAD or NADP as a cofactor, has a high Km for malate and is allosterically activated by fumarate and inhibited by ATP. Cytosolic ME (ME1) and the other mitochondrial ME (ME3) use only NADP as a cofactor and have lower Kms for malate. The assay easily showed for the first time that substantial ME2 activity is present in pancreatic islets of humans, rats and mice and INS-1 832/13 cells. ME2's presence was confirmed with immunoblotting. There was no evidence that ME3 is present in these tissues.

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Figures

Figure 1
Figure 1. ME2 is present in human, rat and mouse pancreatic islets and INS-1 832/13 cells
Immunoblot of islets from individual humans and individual batches of islets from Sprague-Dawley rats or mice (lanes 4 and 7, the NSA strain; lane 5, the C57BL6 strain) and INS-1 832/13 cells with 20 μg protein/lane probed with anti-human ME2 antibody. The blot was additionally probed with anti-beta actin antibody to show equal loading of protein across lanes.
See this image and copyright information in PMC

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