Isolation and characterization of human breast milk lipoamidase

Co-purification of human serum lipoamidase and biotinidase: evidence that the two enzyme activities are due to the same enzyme protein

“…A similar enzyme was described in baker's yeast [5], and later in rabbit and rat tissues [6,7]. The enzyme was identified in human serum [8][9][10] and breast milk [11], by the use of lipoyl-p-aminobenzoic acid (lipoyl-PABA) as an artificial substrate, and the enzyme from breast milk was shown to have a serine residue in the active site [11]. Lipoamidase activity was also found in guinea-pig liver [12] and brain [13], by using lipoyl-PABA as substrate, and was shown to be an integral membrane glycoprotein mainly confined to the microsomal fraction [12].…”

Lipoamidase activity in normal and mutagenized pancreatic cholesterol esterase (bile salt-stimulated lipase)

“…A comparison of the properties of cholesterol esterase and lipoamidase has revealed many similarities between the two proteins. For example, both cholesterol esterase and lipoamidase have been demonstrated to be present in serum, liver and human breast milk [4,[15][16][17][18][19][20]. Both enzymes in the liver have apparent by determining enzyme activity in a mutagenized cholesterol esterase with a His435-Gln435 substitution.…”

“…The presence of an enzyme in the gastrointestinal tract capable of both ester and amide hydrolysis suggests an important role for this protein in the digestion and absorption processes. molecular masses of 60-70 kDa upon SDS/PAGE [19,21], while cholesterol esterase and lipoamidase activities in human breast milk are associated with proteins of apparent molecular masses of > 130 kDa [4,15,22]. Furthermore, both cholesterol esterase and lipoamidase activities are inhibited by serine-reactive reagents, indicating that serine residues are important for enzyme activity [15,23].…”

“…molecular masses of 60-70 kDa upon SDS/PAGE [19,21], while cholesterol esterase and lipoamidase activities in human breast milk are associated with proteins of apparent molecular masses of > 130 kDa [4,15,22]. Furthermore, both cholesterol esterase and lipoamidase activities are inhibited by serine-reactive reagents, indicating that serine residues are important for enzyme activity [15,23]. Analysis of the amino acid composition of cholesterol esterase and milk lipoamidase has also revealed that both proteins are enriched with proline residues [21].…”

Determination of specific activities and kinetic constants of biotinidase and lipoamidase in LEW rat and Lactobacillus casei (Shirota)

“…Human milk lipoamidase [25] has turned out to have the same amino acid sequence to cholesterol esterase (bile salt-stimulated lipase) [26]. Purified porcine brain lipoamidase is very similar to acetylcholinesterase [19,27], and brain enzyme shows more complex characteristics in the active center [17].…”