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What is Autophosphorylation?

Instructor: Korry Barnes

Korry has a Ph.D. in organic chemistry and teaches college chemistry courses.

What does it mean when a protein undergoes a process known as autophosphorylation? In this lesson we will be discussing what this specific biochemical reaction entails and how it occurs.

The Term 'Automatic'

When you hear the term 'automatic,' what's the first thing that comes to mind? Perhaps it's your car, in the sense that you drive a vehicle with an automatic transmission that doesn't require manual shifting of gears. Maybe you think of a close personal friend who is so reliable you think of them 'automatically' if you are in need.

Well, sometimes chemical reactions in biological cells are referred to as 'automatic.' There are reactions that cells depend on for functioning that are classified as occurring seemingly automatically. Today we'll focus on one such reaction known as autophosphorylation. Let's make it happen!

Definition of Autophosphorylation

Before defining autophosphorylation, let's review a couple of other terms first. A phosphate group is a phosphorous atom that's bonded to four oxygen atoms, with one of the phosphorous-oxygen bonds being a double bond and all the others single.

A generic phosphate group. The ~
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In biochemistry, a protein kinase is a type of enzyme whose specific job is to chemically modify other proteins within a biochemical system by phosphorylating them.

In technical terms, autophosphorylation is a biochemical process in which a phosphate group is added to a protein kinase by the action of the protein kinase itself, which is where the 'auto-' prefix comes into play.

Can you see why autophosphorylation is important? In order for a protein kinase to function properly it has to have a phosphate group to donate in the first place. The phosphate that's donated comes from the process of phosphorylation!

Phosphate Group Origins

At this point we know that autophosphorylation is when a protein kinase acquires a phosphate group, which it in turn donates later in another biochemical reaction. But where does the magical phosphate group come from? Certainly it doesn't just appear out of thin air right?

During the course of autophosphorylation usually the phosphate group is supplied by a very special biochemical compound known as adenosine triphosphate (ATP for short). ATP is a very phosphate-rich compound and is very good at serving as a source of phosphate groups for a number of biochemical processes.

Adenosine triphosphate serves as a source of phosphate groups in a number of biochemical reactions
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Phosphate Group Destination

You might be wondering at this point where the phosphate group goes when it's added to our protein kinase. When a protein kinase undergoes autophosphorylation, the phosphate group that's supplied by ATP goes on an amino acid residue on the kinase itself, specifically a threonine, serine, or tyrosine residue. Amino acids are the building blocks of proteins and when lots and lots of amino acids are bonded together, that's how proteins result.

Threonine, serine, and tyrosine are specific amino acids on the protein kinase that accept the phosphate group supplied by ATP. Let's look at the amino acid tyrosine as an example case. Imagine that this single amino acid is just part of a much larger structure, which is the protein kinase.

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