What is the Difference Between Phycocyanin and Phycoerythrin

The main difference between phycocyanin and phycoerythrin is that phycocyanin is light blue in color while phycoerythrin is red in color. 

Phycocyanin and phycoerythrin are light-harvesting pigments in the phycobiliprotein family. They are accessory pigments to chlorophyll. One can harvest these pigments from microalgae. They have potential health benefits as a nutrient supplement. In addition, they are natural colorants used in food items and cosmetics, and as a reagent for immunological assays.

Key Areas Covered

1. What is Phycocyanin
   • Definition, Features, Importance
2. What is Phycoerythrin
   • Definition, Features, Importance
3. Similarities Between Phycocyanin and Phycoerythrin
   • Outline of Common Features
4. Difference Between Phycocyanin and Phycoerythrin
   • Comparison of Key Differences

Key Terms

Chlorophyll, Phycocyanin, Phycoerythrin

What is Phycocyanin

Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family. It is an accessory pigment to chlorophyll. Phycocyanin is light blue in color, and absorbs orange and red light, particularly near 620 nm. Moreover, phycocyanin emits light at 650 nm. In general, phycocyanin occurs in cyanobacteria, a type of blue-green algae. Phycobiliprotein is also responsible for the blue-green color of the organism. Furthermore, the fluorescing properties of phycocyanin are helpful in immunoassay kits.

Figure 1: Phycocyanin

Phycocyanin increases the efficiency of chlorophyll’s oxygen production under low light conditions as an accessory pigment. In addition, phycocyanin can be isolated from marine organisms with high efficiency and low toxicity. More importantly, as a food, phycocyanin has an anti-oxidative function, anti-inflammatory activity, anti-cancer function, and immune enhancement function.

What is Phycoerythrin

Phycoerythrin is a light-harvesting, pigment-protein complex of the phycobiliprotein family. It occurs in red algae and cryptophytes. The main function of phycoerythrin is to undergo photosynthesis by being an accessory pigment to chlorophyll. The red color of phycoerythrin is due to the prosthetic group, phycoerythrobilin.

Figure 2: Red Algae

Moreover, one of the main characteristic features of phycoerythrin is its shape. Normally, phycoerythrin consists of (αβ) monomers usually organized in a disk-shaped hexamer (αβ)₆, which is the functional unit of the antenna rods, or trimer (αβ)₃. There is a third type of subunit, the γ chain of these typical complexes. In addition, the molecular weight of phycoerythrin is around 240 to 260 kDa.

Similarities Between Phycocyanin and Phycoerythrin

• Phycocyanin and phycoerythrin are two types of photosynthetic pigments of the phycobiliprotein family.
• They are water-soluble with intense colors.
• Extracted pigments have great biotechnological potential due to their intense colors, fluorescent properties, and potential health benefits.
• One can harvest these pigments from microalgae.
• Other than nutritional supplements, phycocyanin and phycoerythrin are natural colorants in foods and cosmetics, and as a reagent for immunological assays.
• However, they are unstable to light and other factors such as low pH values, strong ionic strengths, high temperatures, and the presence of alcohols.

Difference Between Phycocyanin and Phycoerythrin

Definition

Phycocyanin refers to a pigment from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin, while phycoerythrin refers to a red, light-harvesting protein found in cyanobacteria, red algae, and cryptomonads.

Color

In general, phycocyanin is light blue in color while phycoerythrin is red in color.

Occurrence

Phycocyanin occurs in blue-green cyanobacteria while phycoerythrin occurs in red algae.

Conclusion

In brief, phycocyanin and phycoerythrin are two types of accessory pigments to chlorophyll, important in photosynthesis to harvest light. However, phycocyanin is blue in color while phycoerythrin is red in color. In addition, phycocyanin mainly occurs in blue-green cyanobacteria while phycoerythrin occurs in red algae. Therefore, the main difference between phycocyanin and phycoerythrin is their color.

References:

1. Hsieh-Lo, M., Castillo, G., Ochoa-Becerra, M. A., & Mojica, L. (2019, July 3). Phycocyanin and phycoerythrin: Strategies to improve production yield and chemical stability. Algal Research. Retrieved August 17, 2022.

Image Courtesy:

1. “Extracted phycocyanin ” By CyanoLakes – Own Work (CC BY-SA 4.0) via Commons Wikimedia
2. “Gracilaria2 ” By Emoody26 – Own Work (CC BY 3.0) via Commons Wikimedia