The key difference between phycocyanin and phycoerythrin is that phycocyanin is a blue colour photosynthetic pigment that absorbs light at a wavelength of around 620-640 nm, while phycoerythrin is a red colour photosynthetic pigment that absorbs light at a wavelength of around 550-570 nm.
The Phycobiliprotein family is a colored and water-soluble biliprotein found in cyanobacteria, rhodophytes, cryptomonads, and cyanelles. They are mainly divided into three main types depending on spectral properties: allophycocyanin, phycocyanin, and phycoerythrin. Phycocyanin and phycoerythrin pigments play pivotal roles in photosynthesis and other cellular processes. However, these pigments have unique properties.
CONTENTS
1. Overview and Key Difference
2. What is Phycocyanin
3. What is Phycoerythrin
4. Similarities – Phycocyanin and Phycoerythrin
5. Phycocyanin vs. Phycoerythrin in Tabular Form
6. Summary – Phycocyanin vs. Phycoerythrin
What is Phycocyanin?
Phycocyanin is a photosynthetic pigment from the light-harvesting pigment family called phycobiliprotein. This family also has other pigments, including allophycocyanin and phycoerythrin. Phycocyanin is an accessory pigment to chlorophyll in plants. It is water soluble, so it cannot exist within the membrane like carotenoids. Thus, phycocyanin aggregates to form clusters and adhere to the membrane called phycobilisomes. Phycocyanin has a peculiar light blue color. It absorbs orange and red light, particularly at a wavelength of 620 nm, and emits fluorescence at a wavelength of about 650 nm.
Figure 01: Phycocyanin
Phycocyanin is made of two subunits named alpha and beta. It consists of a protein structure to which 1 to 2 linear tetrapyrrole chromophores are chemically attached. The molecular weight of phycocyanin is around 70–110 kDa. Furthermore, phycocyanin has different applications in the industry. It has applications in immunoassay kits, serves as a natural coloring agent in the food and beverage industry, and is valuable for monitoring cyanobacteria biomass.
What is Phycoerythrin?
Phycoerythrin is a photosynthetic pigment from the light-harvesting phycobiliprotein family. It is a red color pigment present in cyanobacteria, red algae, and cryptophytes. Phycoerythrin is also an accessory to the main chlorophyll pigment. The red color in this pigment is due to a prosthetic group called phycoerythrobilin. Phycoerythrin absorbs light at a wavelength of 565 nm and emits light at a wavelength of 573 nm. The molecular weight of phycoerythrin is around 240 to 260 kDa.
Figure 02: Phycoerythrin
Phycoerythrin is composed of (αβ) monomers. Phycoerythrin is normally organized in a disk-shaped trimer (αβ)3 or hexamer (αβ)6. Moreover, these typical complexes also contain a third type of subunit called the γ chain. Additionally, phycoerythrin has various applications. It is employed in laboratories as a fluorescence-based indicator to detect the presence of cyanobacteria and for labeling antibodies in techniques like flow cytometry. Moreover, it is used in microarray assays, ELISAs, and other applications requiring high sensitivity.
What are the Similarities Between Phycocyanin and Phycoerythrin?
- Phycocyanin and phycoerythrin are two different photosynthetic pigments found in certain types of microalgae and cyanobacteria.
- Both pigments belong to the phycoerythrobilin family.
- They are proteins in nature.
- Both pigments are accessory pigments to chlorophyll.
- They are water-soluble.
- They play pivotal roles in photosynthesis and other cellular processes.
What is the Difference Between Phycocyanin and Phycoerythrin?
Phycocyanin is a photosynthetic pigment that absorbs light at a wavelength of around 620-640 nm, while phycoerythrin is a photosynthetic pigment that absorbs light at a wavelength of around 550-570 nm. Thus, this is the key difference between phycocyanin and phycoerythrin. Furthermore, phycocyanin is a blue pigment, while phycoerythrin is a red pigment.
The infographic below presents the differences between phycocyanin and phycoerythrin in tabular form for side-by-side comparison.
Summary – Phycocyanin vs. Phycoerythrin
Phycocyanin and phycoerythrin are two different photosynthetic pigments in the phycobiliprotein family. Phycocyanin is a blue colour pigment, while phycoerythrin is a red colour pigment. Moreover, phycocyanin absorbs light at a wavelength of 620 nm and emits fluorescence at a wavelength of about 650 nm. On the other hand, phycoerythrin absorbs light at a wavelength of 565 nm and emits fluorescence at a wavelength of about 573 nm. So, this summarizes the difference between phycocyanin and phycoerythrin.
Reference:
1. “Phycocyanin – An Overview.” Science Direct. Accessed 29 Sept. 2023.
2. Tan, Hui Teng, et al. “A Review on a Hidden Gem: Phycoerythrin from Blue-Green Algae.” Marine Drugs, U.S. National Library of Medicine.
Image Courtesy:
1. “Phycocyanin hexamer 5mjm” By Mitchso – Data from PDB entry 5MJM, the figure generated in Pymol. (CC BY-SA 4.0) via Commons Wikimedia
2. “R-phycoerythrin 1EYX 2 of 2” By The author of the work, the original authors of the Protein Data Bank (PDB) structural data and the molecular graphics program used (CC BY-SA 3.0) via Commons Wikimedia