- Phycoerythrin is a brilliant red, water-soluble phycobiliprotein pigment found primarily in red algae (Rhodophyta) and some cyanobacteria.
- It belongs to the broader family of phycobiliproteins, which are specialized light-harvesting antennae that aid photosynthesis in aquatic organisms.
- Phycoerythrin is especially abundant in species that inhabit deep or shaded aquatic environments, where it plays a key role in capturing light wavelengths—particularly green and blue-green light (around 495–570 nm)—that penetrate deeper into water but are poorly absorbed by chlorophyll. This pigment’s ability to extend the range of usable light makes it crucial for photosynthetic efficiency in such niches.
- Structurally, phycoerythrin is composed of multiple protein subunits (typically α, β, and sometimes γ chains) to which linear tetrapyrrole chromophores, mainly phycoerythrobilin, are covalently attached. These chromophores are responsible for the vivid red color and fluorescence properties of the protein. The assembled phycoerythrin molecules are organized within larger protein complexes known as phycobilisomes, which are attached to the surface of thylakoid membranes. In the phycobilisome, phycoerythrin is located on the outermost parts, where it absorbs incoming light and efficiently transfers the excitation energy inward—first to phycocyanin, then to allophycocyanin, and finally to chlorophyll a in the photosynthetic reaction center.
- Beyond its photosynthetic role, phycoerythrin is of considerable interest in biotechnology and medicine. Its strong and stable fluorescence makes it one of the brightest naturally occurring fluorophores, widely used in flow cytometry, immunofluorescence assays, fluorescence microscopy, and biosensing applications. The high quantum yield and water solubility of phycoerythrin make it ideal for labeling antibodies and detecting low-abundance targets in complex biological samples. Additionally, the pigment has been studied for its antioxidant, anti-inflammatory, and anticancer properties, with some evidence suggesting that its protein and chromophore components may scavenge reactive oxygen species and modulate immune responses.
- In marine ecology, the presence and concentration of phycoerythrin can be used as a biomarker for the abundance and diversity of cyanobacteria and red algae, particularly in monitoring phytoplankton communities and assessing ocean productivity. Because of its distinct optical properties, instruments such as fluorometers and spectrophotometers can detect phycoerythrin in situ, aiding environmental and oceanographic studies.
- In summary, phycoerythrin is a highly specialized pigment that enhances light absorption for photosynthesis in aquatic environments, particularly where light is scarce or filtered. Its importance spans plant physiology, marine ecology, biotechnology, and biomedical research. With its remarkable optical and biological properties, phycoerythrin continues to be a valuable tool in both fundamental science and applied technologies.
