---
title: "Mevalonate Kinase | Organic Chemistry"
description: "Mevalonate kinase is the enzyme that phosphorylates mevalonate to 5-phosphomevalonate in the mevalonate pathway, a core route for terpenoid biosynthesis."
canonical: "https://fiveable.me/organic-chem/key-terms/mevalonate-kinase"
type: "key-term"
subject: "Organic Chemistry"
unit: "Unit 27"
---

# Mevalonate Kinase | Organic Chemistry

## Definition

Mevalonate kinase is the enzyme in the mevalonate pathway that adds a phosphate to mevalonate, making 5-phosphomevalonate. In Organic Chemistry, it shows how terpenoids are built from simple C5 units.

## What It Is

Mevalonate kinase is the enzyme that phosphorylates mevalonate, turning it into 5-phosphomevalonate in the mevalonate pathway. In Organic Chemistry, that step sits right in the middle of terpenoid biosynthesis, where small carbon fragments are converted into the building blocks for bigger natural products.

The reaction uses ATP as the phosphate donor. Mechanistically, the enzyme helps position mevalonate so its alcohol group can be phosphorylated efficiently, which changes the molecule from a relatively inactive acid into a more reactive phosphorylated intermediate. That extra phosphate is not just a label, it helps drive the pathway forward because the product is set up for the next enzyme-catalyzed transformation.

What comes after this step matters just as much as the step itself. 5-phosphomevalonate is eventually converted into isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), the two C5 units that terpenoids are built from. Once you have IPP and DMAPP, the pathway can keep stacking carbon units to make larger molecules such as sesquiterpenes, diterpenes, sterols, and other isoprenoids.

This is why mevalonate kinase shows up in discussions of biosynthesis rather than simple functional groups. The enzyme is part of a metabolic assembly line, where each step changes the carbon skeleton or its leaving groups so the next reaction can happen. If a step is blocked here, the pathway backs up before the cell can make many downstream terpenoid products.

A common way to think about it is that mevalonate is the raw starting material and mevalonate kinase gives it a chemical tag that prepares it for activation. In a course setting, that means you are not memorizing an isolated enzyme name, you are tracking how phosphate transfer, enzyme specificity, and carbon skeleton construction work together in natural product synthesis.

## Why It Matters

Mevalonate kinase matters because it connects ordinary organic reaction ideas, like phosphorylation and activation, to a real biosynthetic pathway. In terpenoid chemistry, the big question is how living systems build complex carbon frameworks from small C5 units. This enzyme is one of the checkpoints that makes that possible.

It also gives you a clean example of pathway logic. Organic Chemistry often asks you to follow what changes from one intermediate to the next, and here the pattern is easy to see: mevalonate is modified, the modified product can be processed further, and that eventually leads to IPP and DMAPP. If you can trace that sequence, you can make sense of how terpenoids, cholesterol precursors, and other isoprenoids originate.

The term also shows up when you compare biosynthetic routes and think about regulation. Because the pathway is controlled, changes in enzyme activity can affect the availability of downstream molecules like sterols and prenyl groups. That makes mevalonate kinase useful for mechanism questions, pathway mapping, and any prompt that asks why a specific intermediate matters instead of just what it is.

For students, it is a good checkpoint term because it sits between simple structure recognition and full pathway explanation. You have to know what gets added, what the product becomes, and why that matters later in the sequence.

## Connections

### [Mevalonate Pathway](/organic-chem/key-terms/mevalonate-pathway)

Mevalonate kinase is one enzyme inside the mevalonate pathway, so this term makes the most sense when you place it in the full sequence. The pathway takes mevalonate through a series of activation steps before producing IPP and DMAPP. If you know the pathway order, you can see why this kinase is a middle step rather than the final product-forming reaction.

### Terpenoids

Terpenoids are the product family that the mevalonate pathway helps build. Mevalonate kinase does not make a terpenoid by itself, but it helps prepare the carbon units that terpenoids come from. When you study terpenoids, this enzyme is part of the “where do the building blocks come from?” question.

### [Isoprenoids](/organic-chem/key-terms/isoprenoids)

Isoprenoids is another name for the larger class of molecules built from repeating five-carbon units. Mevalonate kinase matters here because it contributes to the formation of those five-carbon precursors. If a question uses isoprenoid instead of terpenoid, the pathway logic is the same.

### [Dimethylallyl Diphosphate](/organic-chem/key-terms/dimethylallyl-diphosphate)

Dimethylallyl diphosphate is one of the two key C5 units produced downstream of the mevalonate pathway. Mevalonate kinase acts several steps earlier, but its phosphorylation step helps set up the chain of reactions that eventually yields DMAPP. That makes DMAPP a good “end point” to keep in mind when tracing the pathway forward.

## On the AP Exam

A quiz item or short-answer question might ask you to identify what mevalonate kinase does in a biosynthetic sequence, then trace the pathway to the C5 building blocks that follow. You may also see it in a reaction order problem, where you match the enzyme to the intermediate it produces. If a prompt gives you a pathway diagram, look for the phosphorylation of mevalonate to 5-phosphomevalonate and explain why that activation step matters.

In a lab or discussion setting, the term may come up when comparing enzyme-controlled steps in natural product synthesis or when connecting pathway disruption to loss of downstream terpenoids. The safest move is to name the substrate, the product, and the broader pathway in one sentence.

## Key Takeaways

- Mevalonate kinase is the enzyme that phosphorylates mevalonate to make 5-phosphomevalonate.
- It is part of the mevalonate pathway, which supplies the precursors for terpenoids and related isoprenoids.
- The step matters because it helps push the pathway toward the C5 units IPP and DMAPP.
- If this enzyme is disrupted, downstream biosynthesis can be affected, including sterol and terpenoid production.
- In Organic Chemistry, the term shows how enzymes activate simple intermediates for later carbon-assembly steps.

## FAQs

### What is mevalonate kinase in Organic Chemistry?

Mevalonate kinase is the enzyme that adds a phosphate group to mevalonate, forming 5-phosphomevalonate. In Organic Chemistry, it appears in the mevalonate pathway, which builds the precursors for terpenoids and isoprenoids. It is one of the activation steps that prepares the molecule for later conversion into IPP and DMAPP.

### What does mevalonate kinase act on?

It acts on mevalonate. The enzyme uses ATP to phosphorylate mevalonate, so the product is 5-phosphomevalonate. That change matters because the pathway needs a more activated intermediate before it can make the five-carbon building blocks used in terpenoid biosynthesis.

### How is mevalonate kinase different from the mevalonate pathway?

The mevalonate pathway is the whole biosynthetic route, while mevalonate kinase is just one enzyme in that route. The pathway includes multiple steps that eventually lead to IPP and DMAPP. Mevalonate kinase is the step that phosphorylates mevalonate early in the process.

### Why does mevalonate kinase matter for terpenoids?

Terpenoids are built from repeating five-carbon units, and those units come from the mevalonate pathway. Mevalonate kinase helps move the pathway toward those units by activating mevalonate. Without that step, the cell would have a harder time making the downstream molecules needed for terpenoid synthesis.

## Related Study Guides

- [27.5 Terpenoids](/organic-chem/unit-27/terpenoids/study-guide/Idk5pyf48ZWPIP7F)

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