This step is the enzymatic transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP by phosphoglycerate kinase , forming ATP and 3-phosphoglycerate . At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP), this reaction does not occur. Because ATP decays relatively quickly when it is not metabolized, this is an important regulatory point in the glycolytic pathway.
Hypothalamic expression of the GCK gene plays an important role in the regulation of dietary glucose intake in particular, and overall feeding behavior in general. The primary hypothalamic cells expressing glucokinase are within the arcuate nucleus, ARC. Expression of the hypothalamic GCK gene increases specifically within the ARC in response to fasting. Manipulation of GCK expression within the ARC of experimental animals alters glucose intake. Increased GCK expression in the ARC results in increased glucose ingestion, whereas, decreased GCK expression results in reduced glucose ingestion. These observations indicate that ARC expression of GCK underlies the phenomenon of carbohydrate craving.