Macrophage Ecto-Enzymes: Their Identification, Metabolism, and Control
Ecto-enzymes are enzymes which are associated with the plasma membrane in such a way that their active sites are accessible to the external environment. They are special examples of a more general class of proteins which are associated with the outer face of the plasma membrane and which may be called ‘ecto-proteins’. These proteins are operationally recognized in a variety of ways (Table 1), either because they act as binding sites or receptors for various ligands, because they express enzymatic activity, or because an antibody has been prepared to which they bind. An association of a number of enzymes with the plasma membrane of phagocytes has been established (Table 2) and several of them have been identified as ecto-enzymes by the use of some of the techniques listed in Table 3.
KeywordsAdenosine Fractionation Lysine Histamine Trypsin
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