# A structural perspective on α‐glucan catabolism in oxygenic phototrophs

## TL;DR

This review explains how oxygenic phototrophs break down starch and glycogen using enzymes, focusing on structural insights into their regulation and function.

## Contribution

The paper integrates recent structural studies to reveal how enzyme architecture and regulation control carbon mobilization in photosynthetic organisms.

## Key findings

- Structural studies reveal how enzymes recognize substrates and transition between active and inactive states.
- Regulatory elements like redox switches and protein–protein interactions modulate enzyme activity.
- These insights explain how oxygenic phototrophs manage carbon storage under fluctuating conditions.

## Abstract

Starch and glycogen are the main α‐glucan storage polymers in oxygenic photoautotrophs, ensuring metabolic continuity during day/night cycles and environmental stress. Their mobilization requires a suite of catabolic enzymes whose activities are tightly regulated to balance carbon storage with energy demands. Recent structural studies have provided key mechanistic insights into how these enzymes recognize their substrates, transition between active and inactive states, and respond to cellular signals. In this review, we summarize advances in the structural biology of starch and glycogen degradation in plant chloroplasts and cyanobacteria. We highlight the architectural features that determine substrate specificity and examine how regulatory elements, such as redox switches, proteolytic events, and protein–protein interactions modulate enzyme activity. These structural and mechanistic insights inform how oxygenic phototrophs manage carbon storage to ensure survival under fluctuating environmental conditions.

Efficient mobilization of carbon storage polymers is essential for the survival of oxygenic phototrophs under fluctuating environmental conditions. Recent structural studies have uncovered the molecular mechanisms that govern starch and glycogen degradation in photosynthetic organisms. This review integrates these advances to highlight how enzyme architecture and regulation orchestrate carbon mobilization in plant chloroplasts and cyanobacteria.