Simple, single-membrane organelle

Function in photorespiration & oil mobilization

This electron micrograph shows four microbodies (arrows) tightly appressed to the chloroplasts in soybean (Glycine max) mesophyll cells. It reflects the cooperation between these two kinds of organelles in photosynthesis. The function of the microbodies in leaf cells is to participate in the oxidation of glycolates to glyoxylate that produces H₂O₂ (hydrogen peroxide), which in turn is destroyed by the enzyme catalase. This process is called photorespiration because it occurs only in the light. This represents an inefficiency of rubisco (an acronym for the enzyme ribulose 1,5 biphosphate carboxylase), which accepts oxygen instead of the normal substrate CO₂ when O₂ accumulates to high concentrations. The oxygen-rich rubisco is tricked into releasing CO₂.

In contrast to plastids and mitochondria, microbodies are bounded by a single membrane, have no internal membrane structure, lack DNA and are amorphous internally (as shown here) or, in some cases, may have protein crystals internally which represent stored enzymes such as catalase. Like plastids and mitochondria, microbodies multiply by a type of fission division.

A different population of microbodies are key organelles in oil-storing cells of seeds where they are involved in the conversion of oil into carbohydrates during seed germination.