Glycolysis Enzymes: Difference between revisions
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The first phase of glycolysis is sometimes referred to as the "investment phase", where ATP is consumed to set up later, energy generating steps. | The first phase of glycolysis is sometimes referred to as the "investment phase", where ATP is consumed to set up later, energy generating steps. | ||
The first step of the pathway is the conversion of <scene name=' | The first step of the pathway is the conversion of <scene name='94/942621/Cv/4'>glucose</scene> to <scene name='94/942621/Cv/5'>glucose-6-phosphate</scene> by either hexokinase or glucokinase. Hexokinases should not be confused with glucokinase, which is a specific isoform of hexokinase. All hexokinases are capable of phosphorylating several hexoses but glucokinase acts with a 50-fold lower substrate affinity and its main hexose substrate is glucose.[https://en.wikipedia.org/wiki/Hexokinase] | ||
'''Step 2: Phosphoglucose isomerase''' | '''Step 2: Phosphoglucose isomerase''' | ||
<scene name=' | <scene name='94/942621/Cv/5'>Glucose-6-phosphate</scene> isomerizes to <scene name='39/392339/Cv1/1'>fructose-6-phosphate</scene>; this reaction is catalyzed by [[Stancu_Phosphoglucoisomerase_Sandbox_1|phosphoglucoisomerase]]. This isomerization allows for the creation of two, three carbon sugars as a product. | ||
*[[Phosphoglucose isomerase]] | *[[Phosphoglucose isomerase]] | ||
Rabbit <scene name='48/481605/Cv/6'>PGI active site containing the substrate D-fructose 6-phosphate shows the substrate interacting mainly with residues of one subunit</scene><ref>PMID:11425306</ref>. Water molecules are shown as red spheres. | Rabbit <scene name='48/481605/Cv/6'>PGI active site containing the substrate D-fructose 6-phosphate shows the substrate interacting mainly with residues of one subunit</scene><ref>PMID:11425306</ref>. Water molecules are shown as red spheres. | ||
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'''Step 9: Phosphopyruvate hydratase (enolase)''' | '''Step 9: Phosphopyruvate hydratase (enolase)''' | ||
A second high energy intermediate, | A second high energy intermediate, <scene name='39/392339/Cv1/8'>phosphoenolpyruvate</scene>, is formed by [[Enolase]]. | ||
'''Step 10: Pyruvate kinase''' | '''Step 10: Pyruvate kinase''' | ||
The final reaction of the pathway is catalyzed by [[Pyruvate Kinase|pyruvate kinase]], which converts phosphoenolpyruvate to <scene name='39/392339/ | The final reaction of the pathway is catalyzed by [[Pyruvate Kinase|pyruvate kinase]], which converts phosphoenolpyruvate to <scene name='39/392339/Cv1/11'>pyruvate</scene>, while generating ATP from ADP. | ||
==The fates of pyruvate== | ==The fates of pyruvate== | ||
Under oxidative conditions, pyruvate continues to be metabolized through the [[The_Citric_Acid_Cycle|tricarboxylic acid cycle]]. While energy can be obtained under anaerobic conditions from glycolysis alone, the accumulation of pyruvate and NADH limits this. There are two main strategies for dealing with this problem. | Under oxidative conditions, pyruvate continues to be metabolized through the [[The_Citric_Acid_Cycle|tricarboxylic acid cycle]]. While energy can be obtained under anaerobic conditions from glycolysis alone, the accumulation of pyruvate and NADH limits this. There are two main strategies for dealing with this problem. In most cells, [[Lactate_Dehydrogenase|lactate dehydrogenase]] converts the <scene name='39/392339/Cv1/11'>pyruvate</scene> and NADH to <scene name='39/392339/Cv1/10'>lactate</scene>, dealing with both problems at once and regenerating NAD+ so glycolysis can continue. <scene name='Lactate_Dehydrogenase/Cv/4'>Conversion of pyruvate into lactate acid</scene>. Fortunately for us, some yeast cells do something else--leading to the generation of ethanol. First, [[Pyruvate decarboxylase|pyruvate decarboxylase]] catalyzes the converstion from pyruvate to acetaldehyde, releasing carbon dioxide. Next, aldehyde dehydogenase reduces the acetaldehyde to ethanol, converting NADH to NAD+ in the process. | ||
==Additional Resources== | ==Additional Resources== | ||