Definition for Periplasmic space
From Biology Forums Dictionary
The periplasmic space or periplasm is a space between the inner cytoplasmic membrane and external outer membrane of Gram-negative bacteria or the equivalent space outside the inner membrane of Gram-positive bacteria. It may constitute up to 40% of the total cell volume in Gram-negative species, and is drastically smaller in Gram-positive species. The space contains a loose network of murein (peptidoglycan) chains, as well as a gel containing hydrolytic and degradative enzymes. In addition, it includes nutrient binding and transport proteins, hydrolytic proteins, and antibiotic resistance proteins. Other enzymes in the gel are involved in various biochemical pathways including peptidoglycan synthesis, electron transport, and alteration of substances toxic to the cell (xenobiotic metabolism). In some species, the gel also contains beta-lactamase, an enzyme responsible for degrading penicillin. This can be of clinical importance when considering antibiotic resistance.