The periplasmic space or periplasm is a space between the inner cell membrane and outer membrane at gram negative bacteria or the equivalent space outside the inner membrane at gram positive bacteria. It can reach up to 40% of cell volume at gram negative species, but is significantly less at gram-positive. The periplasm contains a loose network of murein (peptidoglycan), as well as a gel which contains many periplasmic proteins. These include hydrolytic enzymes, binding proteins for the ABC transport and chemical receptors for the chemotaxis. Other enzymes in the periplasm are involved in various biochemical pathways, such as peptidoglycan synthesis, electron transport and xenobiotic metabolism. The outer membrane therefore has the main function of keeping those periplasmic proteins close to the cell. In some bacteria, the periplasm also contains beta-lactamase, an enzyme responsible for the breakdown of penicillin. This can be of clinical importance when talking about antibiotic resistance. Construction of a gram-negative cell wall Other use
In yeast, the term "periplasmic space" refers to the thin region between the plasma membrane and the cell wall. (In bacteria it's a part of the cell wall) More info
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