Human milk bile‐salt stimulated lipase Sequence similarity with rat lysophospholipase and homology with the active site region of cholinesterases

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Abstract
To determine the active site residue, human milk bile‐salt stimulated lipase (BSSL) was labelled with [3H]diisopropyl fluorophosphate (DFP). Partial sequence analysis or cyanogen bromide fragments (a total of 146 residues from 6 peptides) revealed 84% sequence identity with a putative rat lysophospholipase. Sequence analysis of a [3H]DFP‐labelled peptide indicated that the active site serine was contained in the sequence Gly‐Glu‐Scr‐Ala‐Gly. In addition to similarity with rat lysophospholipase, this sequence showed homology with regions of human butyrylcholinesterase and electric ray acetylcholinesterase (68% identity). It is concluded that these proteins are members of a new supergene family.