# CBDA synthase

> CBDA synthase is the trichome enzyme that converts CBGA into CBDA; it competes with THCA synthase, and its alleles largely decide whether a plant is CBD-dominant.

- Canonical: https://genetixbay.com/knowledge/glossary/cbda-synthase.html
- Also written: CBDAS, CBDA synthase gene, cannabidiolic acid synthase, CBD synthase
- Glossary category: Cannabinoids and terpenes · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

CBDA synthase (CBDAS) is the oxidocyclase enzyme that converts [CBGA](https://genetixbay.com/knowledge/glossary/cbga.md) into [CBDA](https://genetixbay.com/knowledge/glossary/cbda.md). Taura and colleagues characterised it in 2007 and described it as the chemotype-determining enzyme in fibre-type cannabis. It sits in the same genomic region as [THCA synthase](https://genetixbay.com/knowledge/glossary/thca-synthase.md) and competes for the same CBGA pool.

## In practice

Hemp-type and CBD-type plants carry functional CBDAS and typically non-functional or absent THCAS. Crossing a THC-type plant with a CBD-type plant produces [F1](https://genetixbay.com/knowledge/glossary/f1.md) offspring that are usually balanced (roughly 1:1), and an F2 that segregates into THC-type, balanced and CBD-type plants. Real ratios drift from textbook Mendelian numbers because the synthase region contains several linked gene copies and some partially active alleles. Even CBD-dominant plants produce a little [THCA](https://genetixbay.com/knowledge/glossary/thca.md), because CBDAS isn't perfectly specific; that matters for anyone growing [hemp](https://genetixbay.com/knowledge/glossary/hemp.md) under a [THC](https://genetixbay.com/knowledge/glossary/thc.md) limit.

## Don't confuse with

- **THCA synthase**: the competing enzyme.
- **CBD**: the neutral form, made later by decarboxylation.
- **CBGA**: the substrate, not the enzyme.

## Related terms

[THCA synthase](https://genetixbay.com/knowledge/glossary/thca-synthase.md), [CBGA](https://genetixbay.com/knowledge/glossary/cbga.md), [CBDA](https://genetixbay.com/knowledge/glossary/cbda.md), [Chemotype ratio](https://genetixbay.com/knowledge/glossary/chemotype-ratio.md), [CBD](https://genetixbay.com/knowledge/glossary/cbd.md)

## Read more

- [Chemotype inheritance: how THC and CBD synthase alleles pass on](https://genetixbay.com/knowledge/breeding/chemotype-inheritance.md)
- [Genotyping: what a DNA test can and can't prove](https://genetixbay.com/knowledge/breeding/genotyping-what-tests-prove.md)

## Sources

1. Taura F, Sirikantaramas S, Shoyama Y, et al. 2007. Cannabidiolic-acid synthase, the chemotype-determining enzyme in the fiber-type Cannabis sativa. FEBS Letters 581(16):2929-2934.
2. Gülck T, Møller BL. 2020. Phytocannabinoids: origins and biosynthesis. Trends in Plant Science 25(10):985-1004.