Dynamin enzyme, molecular model. The two protein chains that form a pleckstrin homology (PH) domain can be seen (blue and pink). Domains are structural regions of enzymes that are often actively involved in biological processes. Dynamin is primarily responsible for facilitating the absorption of material from outside the cell (endocytosis) in eukaryotic cells. Dynamin's PH domain is thought to play an important role in the enzyme's function in endocytosis.