Glycosyl hydrolases family 18.

Predicted glycosyl hydrolase [General function prediction only]

Glyco_18 domain.

Cortical fragment-lytic enzyme (CFLE) is a peptidoglycan hydrolase involved in bacterial endospore germination. CFLE is expressed as an inactive preprotein (called SleB) in the forespore compartment of sporulating cells. SleB translocates across the forespore inner membrane and is deposited as a mature enzyme in the cortex layer of the spore. As part of a sensory mechanism capable of initiating germination, CFLE degrades a spore-specific peptidoglycan constituent called muramic-acid delta-lactam that comprises the outer cortex. CFLE has a C-terminal glycosyl hydrolase family 18 (GH18) catalytic domain as well as two N-terminal LysM peptidoglycan-binding domains. In addition to SleB, this family includes YaaH, YdhD, and YvbX from Bacillus subtilis.

Stabilin-1 interacting chitinase-like protein (SI-CLP) is a eukaryotic chitinase-like protein of unknown function that interacts with the endocytic/sorting transmembrane receptor stabilin-1 and is secreted from the lysosome. SI-CLP has a glycosyl hydrolase family 18 (GH18) domain but lacks a chitin-binding domain. The catalytic amino acids of the GH18 domain are not conserved in SI-CLP, similar to the chitolectins YKL-39, YKL-40, and YM1/2. Human SI-CLP is sorted to late endosomes and secretory lysosomes in alternatively activated macrophages.