--- title: "Pyruvate Kinase | General Biology I" description: "Pyruvate kinase is a glycolysis enzyme that converts PEP to pyruvate and makes ATP, a final energy-payoff step in General Biology I." canonical: "https://fiveable.me/college-bio/key-terms/pyruvate-kinase" type: "key-term" subject: "General Biology I" unit: "Unit 7" --- # Pyruvate Kinase | General Biology I ## Definition Pyruvate kinase is the enzyme in glycolysis that converts phosphoenolpyruvate (PEP) into pyruvate while making ATP from ADP. In General Biology I, it marks the last energy-producing step of glycolysis. ## What It Is Pyruvate kinase is the enzyme that finishes glycolysis by turning phosphoenolpyruvate, or PEP, into pyruvate and transferring a phosphate to ADP to make ATP. In General Biology I, this is the last step of the pathway and one of the clearest examples of substrate-level phosphorylation, where a phosphate is moved directly to ADP without the electron transport chain. That reaction matters because PEP is a very high-energy molecule. When pyruvate kinase removes its phosphate group, the energy released is enough to power ATP formation. So this step is not just "making pyruvate," it is the payoff for the earlier investment of energy that helped prepare glucose for breakdown. This enzyme sits near the end of the energy payoff phase of glycolysis. By the time the pathway reaches pyruvate kinase, the sugar has already been split into two three-carbon molecules and processed through several steps that captured energy in usable form. Pyruvate kinase takes one of the last chances to extract ATP directly from the carbon skeleton before glycolysis ends. The product, pyruvate, can go in different directions depending on oxygen availability and what the cell needs next. If oxygen is available, pyruvate can move toward aerobic respiration. If oxygen is limited, pyruvate can be used in fermentation instead. That means pyruvate kinase sits at a metabolic crossroads, even though its own job is very specific. Cells do not leave this enzyme running at full speed all the time. Pyruvate kinase is regulated allosterically, which means molecules bind somewhere other than the active site and change how well it works. In a simplified course example, fructose-1,6-bisphosphate activates pyruvate kinase, while ATP can inhibit it when the cell already has plenty of energy. That gives glycolysis a feedback loop, so the pathway slows down when ATP is abundant and speeds up when the cell needs more. ## Why It Matters Pyruvate kinase matters because it connects the chemistry of glycolysis to the cell’s energy output. If you are tracing where ATP comes from, this is one of the exact steps you point to. It is also a good checkpoint for understanding why glycolysis is not just "glucose gets broken down," but a controlled pathway with steps that are chemically and biologically distinct. This enzyme also helps explain regulation. General Biology I often asks why a pathway speeds up or slows down, and pyruvate kinase is a clean example of feedback tied to energy state. When ATP is high, the cell does not need as much more sugar breakdown, so pyruvate kinase activity can drop. When earlier glycolytic intermediates signal that the pathway is underway, the enzyme can be activated to keep carbon flowing to pyruvate. Pyruvate kinase also helps you connect glycolysis to later topics like cellular respiration and fermentation. The pyruvate it produces is the branch point, so if you understand this enzyme, it becomes easier to follow what happens after glycolysis ends. In practice, this makes it a useful anchor term for lab observations, pathway diagrams, and short-answer questions about cellular energy. ## Connections ### glycolysis Pyruvate kinase is one step in glycolysis, specifically the last reaction of the pathway. If you map glycolysis from glucose to pyruvate, this enzyme sits at the end of the energy payoff phase and helps show how the pathway produces a net gain of ATP. ### ATP Pyruvate kinase makes ATP directly from ADP in a substrate-level phosphorylation step. It is also regulated by ATP, which can signal that the cell already has enough energy and slow the pathway down. ### allosteric regulation This enzyme is a classic example of allosteric regulation because molecules can bind away from its active site and change its activity. Fructose-1,6-bisphosphate can activate it, while ATP can inhibit it, which ties enzyme activity to the cell’s metabolic state. ### [fructose-1,6-bisphosphate](/college-bio/key-terms/fructose-16-bisphosphate) Fructose-1,6-bisphosphate is an upstream glycolysis intermediate that can activate pyruvate kinase. That means a molecule made earlier in the pathway helps push the later steps forward, creating a feed-forward style of control. ## On the AP Exam A quiz or diagram question may ask you to label the last ATP-producing step of glycolysis, identify the enzyme that converts PEP to pyruvate, or explain why ATP can inhibit the pathway. In a pathway problem, you might need to trace what happens before and after pyruvate kinase and name pyruvate as the product that continues into respiration or fermentation. In a lab or short-answer prompt, you could be asked to connect enzyme regulation to a cell’s energy state, especially if the question shows a glycolysis diagram with activators and inhibitors. The safest move is to name the substrate, product, and type of energy transfer, then link that to the pathway’s overall purpose. ## pyruvate kinase vs pyruvate Pyruvate kinase is the enzyme that makes pyruvate, while pyruvate is the three-carbon product of the reaction. If a question asks for the catalyst, name the enzyme. If it asks for the molecule that leaves glycolysis, name pyruvate. ## Key Takeaways - Pyruvate kinase is the enzyme that converts PEP to pyruvate in the final step of glycolysis. - This reaction makes ATP directly from ADP, so it is a substrate-level phosphorylation step. - The enzyme is regulated by the cell’s energy state, including activation by fructose-1,6-bisphosphate and inhibition by ATP. - Pyruvate kinase sits at the end of the energy payoff phase, where glycolysis finally returns energy to the cell. - Its product, pyruvate, can keep going into aerobic respiration or fermentation depending on oxygen availability. ## FAQs ### What is pyruvate kinase in General Biology I? Pyruvate kinase is the glycolysis enzyme that converts phosphoenolpyruvate, or PEP, into pyruvate while making ATP from ADP. It is the last ATP-producing step of glycolysis, so it is often used to show how the pathway ends with both energy capture and pyruvate production. ### Does pyruvate kinase make ATP? Yes. It makes ATP directly in the reaction that turns PEP into pyruvate. This is different from the electron transport chain, because the phosphate moves straight from a high-energy substrate to ADP. ### What activates pyruvate kinase? A common activator is fructose-1,6-bisphosphate, an earlier glycolysis intermediate. That kind of activation helps the pathway keep moving when glucose breakdown is already underway. ### Is pyruvate kinase the same as pyruvate? No. Pyruvate kinase is the enzyme, and pyruvate is the product it makes. That distinction shows up a lot on diagrams and multiple-choice questions, so it helps to separate the catalyst from the molecule being produced. ## Related Study Guides - [7.2 Glycolysis](/college-bio/unit-7/2-glycolysis/study-guide/XvpWhCdJCs2gWC9n) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/college-bio/key-terms/pyruvate-kinase#resource","name":"Pyruvate Kinase | General Biology I","url":"https://fiveable.me/college-bio/key-terms/pyruvate-kinase","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/college-bio/key-terms/pyruvate-kinase#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:21:10.328Z","isPartOf":{"@type":"Collection","name":"General Biology I Key Terms","url":"https://fiveable.me/college-bio/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/college-bio/key-terms/pyruvate-kinase#term","name":"pyruvate kinase","description":"Pyruvate kinase is the enzyme in glycolysis that converts phosphoenolpyruvate (PEP) into pyruvate while making ATP from ADP. 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