Glucokinase pancreas

Figure 3.20 A plot of the percentage of maximal activity of glucokinase and hexokinase against the glucose concentration. Hexokinase is present in most if not all cells. Glucokinase is only present in hepatocytes and p-cells of the Islets of Langerhans in the pancreas (known as the endocrine pancreas). The enzyme is physiologically very important in both tissues e.g. a low activity in the p-cells can be a cause of one type of diabetes mellitus.

Hexokinases, the enzymes that catalyze the phosphorylation of glucose, are a family of tissue-specific isoenzymes that differ in their kinetic properties. The isoenzyme found in liver and p cells of the pancreas has a much higher than other hexokinases and is called glucokinase. In many cells, some of the hexokinase is bound to porins in the outer mitochondrial membrane (voltage-dependent anion channels see Chapter 21), which gives these enzymes first access to newly synthesized ATP as it exits the mitochondria. 

Assume that an increase in blood glucose concentration from 5 to 10 mM would result in insulin release by the pancreas. A mutation in pancreatic glucokinase can lead to MODY because of which of the following within the pancreatic 3-cell ... 

Glucokinase is expressed only in liver and the (3-cells of the pancreas it has a for glucose of 20 mmol/L. 

What conclusions can you draw from this information about the probable role of glucokinase in the P-cells of the pancreas ... 

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