Glyoxysomes are specialized peroxisomes found in plants (particularly in the fat

Fat

Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

 storage tissues of germinating

Germination

Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

 seeds) and also in filamentous fungi.
As in all peroxisomes, in glyoxysomes the fatty acids are hydrolyzed to acetyl-CoA

Acetyl-CoA

Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester...

 by peroxisomal β-oxidation enzymes. Besides peroxisomal functions, glyoxysomes possess additionally the key enzymes of glyoxylate cycle

Glyoxylate cycle

The glyoxylate cycle, a variation of the Tricarboxylic Acid Cycle, is an anabolic metabolic pathway occurring in plants, bacteria, protists, fungi and several microorganisms, such as E. coli and yeast. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of...

 (isocitrate lyase

Isocitrate lyase

Isocitrate lyase , or ICL, is an enzyme in the glyoxylate cycle that catalyzes the cleavage of isocitrate to succinate and glyoxylate. Together with malate synthase, it bypasses the two decarboxylation steps of the tricarboxylic acid cycle and is used by bacteria, fungi, and plants.The systematic...

 and malate synthase

Malate synthase

In enzymology, a malate synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are acetyl-CoA, H2O, and glyoxylate, whereas its two products are -malate and CoA....

) which accomplish the glyoxylate cycle

Glyoxylate cycle

The glyoxylate cycle, a variation of the Tricarboxylic Acid Cycle, is an anabolic metabolic pathway occurring in plants, bacteria, protists, fungi and several microorganisms, such as E. coli and yeast. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of...

 bypass.

Thus, glyoxysomes (as all peroxisomes) contain enzymes that initiate the breakdown of fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

s and additionally possess the enzymes to produce intermediate products for the synthesis of sugars by gluconeogenesis

Gluconeogenesis

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids....

. The seedling uses these sugars synthesized from fats until it is mature enough to produce them by photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

.