AGAT Enzyme — Glossary | Creatine.my

Written by Creatine.my Editorial Team · · 3 min read
3 min read

What is AGAT?

AGAT (arginine:glycine amidinotransferase, also called GATM) is the enzyme responsible for the first step of endogenous creatine synthesis.

It catalyzes the transfer of an amidino group from arginine to glycine, producing guanidinoacetate (GAA) and ornithine.

This reaction occurs primarily in the kidneys.

AGAT is the rate-limiting enzyme in creatine biosynthesis, meaning it controls how fast your body produces creatine naturally.

The body produces approximately 1-2g of creatine per day through this pathway.

The Biosynthesis Pathway

Creatine synthesis is a two-step process spanning two organs:

  1. Step 1 (Kidney — AGAT): Arginine + Glycine → Guanidinoacetate (GAA) + Ornithine
  2. Step 2 (Liver — GAMT): GAA + S-adenosylmethionine → Creatine + S-adenosylhomocysteine

GAA produced by AGAT in the kidneys travels through the bloodstream to the liver, where the GAMT enzyme completes the synthesis by adding a methyl group.

Relevance to Creatine Supplementation

Understanding AGAT helps explain why supplementation is beneficial: endogenous production (1-2g/day) is often insufficient for optimal muscle saturation, especially for athletes and those with higher demands.

Supplementation bypasses the AGAT-GAMT pathway entirely, delivering creatine directly for transport into cells.

Sources & References

Full citations available in our Research Library.

Frequently Asked Questions

What does the AGAT enzyme do?

AGAT (arginine:glycine amidinotransferase) catalyzes the first step of creatine synthesis in the body. It combines arginine and glycine in the kidneys to produce guanidinoacetate (GAA), which is then converted to creatine by the GAMT enzyme in the liver.

Where is AGAT found in the body?

AGAT is primarily expressed in the kidneys, though it is also found in smaller amounts in the pancreas and brain. The kidney location is why kidney function plays a role in endogenous creatine production.

Can AGAT deficiency be treated with creatine supplementation?

Yes. AGAT deficiency is a rare genetic disorder that impairs creatine synthesis. Unlike creatine transporter deficiency, AGAT deficiency responds well to oral creatine supplementation because the transporter is still functional — the body simply cannot make enough creatine on its own.

Reviewed by T. Dinaiz, BSc (Molecular Biology), MSc (Biotechnology)

Reviewed against peer-reviewed research · Our editorial policy