Sandbox 172: Difference between revisions

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Hexokinase Type I is considered an enzyme of maintenence; it is unaffected by most physiological, metabolic and hormonal changes within the biological system.<ref>Henningsen C., Thaiss F., Zahner G. High glucose induces type I hexokinase gene expression in isolated glomeruli of diabetic rats and in mesangial cells. Nephron Physiology. 2003.'''93''':67-75.</ref> Hexokinase Type I is mainly found in mammalian tissues; it is crucial enzyme in maintaining a downward concentration gradient to provide a steady influx of glucose into cells.<ref name="two" />

==Introduction==

Four types of hexokinase isozymes exist in the human biological system. They all serve to catalyze the exact same reaction in glycolysis even though they are encoded by different sets of genes. The hexokinase types I-III all have a high affinity for glucose and become subject to inhibition in the presence of glucose-6-phosphate- the first step reaction product in glycolysis. Hexokinase type I is the predominant form in the muscle while hexokinase type II is the predominant form in myocytes. Hexokinase type IV varies from the other three hexokinase types as it is not inhibited by the production of glucose-6-phosphate and shows a lower affinity for glucose. Hexokinase type I and II have the particular ability to bind to outer mitochondrial membrane, this binding happens both specifically and reversibly.<ref name="one">Garavito R., Mulichuk A., Padmanabhan K., Wilson J. The structure of mammalian hexokinase-1. Nature Structural and Molecular Biology. 1998. '''5''': 555-560.</ref>

Four types of hexokinase isozymes exist in the human biological system. They all serve to catalyze the exact same reaction in glycolysis even though they are encoded by different sets of genes. The hexokinase types I-III all have a high affinity for glucose and become subject to inhibition in the presence of glucose-6-phosphate- the first step reaction product in glycolysis.<ref name="two" /> Hexokinase type I is the predominant form in the muscle while hexokinase type II is the predominant form in myocytes. Hexokinase type IV varies from the other three hexokinase types as it is not inhibited by the production of glucose-6-phosphate and shows a lower affinity for glucose. Hexokinase type I and II have the particular ability to bind to outer mitochondrial membrane, this binding happens both specifically and reversibly.<ref name="one">Garavito R., Mulichuk A., Padmanabhan K., Wilson J. The structure of mammalian hexokinase-1. Nature Structural and Molecular Biology. 1998. '''5''': 555-560.</ref>

==Structural Overview==

The size of hexokinase type I is approximately 100 kD.<ref>Fromm H., Zewe V. Kinetic studies of the brain hexokinase reaction. The Journal of Biological Chemistry. 1962.'''235''':1661-1667.</ref> Hexokinase type I is constructed by a N-terminal regulatory domain and a C-terminal catalytic domain joined together by an alpha helix. The glucose binding site of hexokinase type I can be found within the two sub-units that make up the isoenzyme, these are known as lobes. Factors that contribute to the binding of glucose to this active site include amino acids within the actual site and hydrogen bonding that takes place on the glucose between the hydroxyl groups.

Sandbox 172: Difference between revisions

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@@ Line 5: / Line 5: @@
 Hexokinase Type I is considered an enzyme of maintenence; it is unaffected by most physiological, metabolic and hormonal changes within the biological system.<ref>Henningsen C., Thaiss F., Zahner G. High glucose induces type I hexokinase gene expression in isolated glomeruli of diabetic rats and in mesangial cells. Nephron Physiology. 2003.'''93''':67-75.</ref> Hexokinase Type I is mainly found in mammalian tissues; it is crucial enzyme in maintaining a downward concentration gradient to provide a steady influx of glucose into cells.<ref name="two" />
 ==Introduction==
-Four types of hexokinase isozymes exist in the human biological system. They all serve to catalyze the exact same reaction in glycolysis even though they are encoded by different sets of genes. The hexokinase types I-III all have a high affinity for glucose and become subject to inhibition in the presence of glucose-6-phosphate- the first step reaction product in glycolysis. Hexokinase type I is the predominant form in the muscle while hexokinase type II is the predominant form in myocytes. Hexokinase type IV varies from the other three hexokinase types as it is not inhibited by the production of glucose-6-phosphate and shows a lower affinity for glucose. Hexokinase type I and II have the particular ability to bind to outer mitochondrial membrane, this binding happens both specifically and reversibly.<ref name="one">Garavito R., Mulichuk A., Padmanabhan K., Wilson J. The structure of mammalian hexokinase-1. Nature Structural and Molecular Biology. 1998. '''5''': 555-560.</ref>
+Four types of hexokinase isozymes exist in the human biological system. They all serve to catalyze the exact same reaction in glycolysis even though they are encoded by different sets of genes. The hexokinase types I-III all have a high affinity for glucose and become subject to inhibition in the presence of glucose-6-phosphate- the first step reaction product in glycolysis.<ref name="two" /> Hexokinase type I is the predominant form in the muscle while hexokinase type II is the predominant form in myocytes. Hexokinase type IV varies from the other three hexokinase types as it is not inhibited by the production of glucose-6-phosphate and shows a lower affinity for glucose. Hexokinase type I and II have the particular ability to bind to outer mitochondrial membrane, this binding happens both specifically and reversibly.<ref name="one">Garavito R., Mulichuk A., Padmanabhan K., Wilson J. The structure of mammalian hexokinase-1. Nature Structural and Molecular Biology. 1998. '''5''': 555-560.</ref>
 ==Structural Overview==
 The size of hexokinase type I is approximately 100 kD.<ref>Fromm H., Zewe V. Kinetic studies of the brain hexokinase reaction. The Journal of Biological Chemistry. 1962.'''235''':1661-1667.</ref> Hexokinase type I is constructed by a N-terminal regulatory domain and a C-terminal catalytic domain joined together by an alpha helix. The glucose binding site of hexokinase type I can be found within the two sub-units that make up the isoenzyme, these are known as lobes. Factors that contribute to the binding of glucose to this active site include amino acids within the actual site and hydrogen bonding that takes place on the glucose between the hydroxyl groups.