Microsomal methionine aminopeptidase: Properties of the detergent-solubilized enzyme

Removal of N-terminal methionine from haemoglobin nascent peptides by a membrane-bound rat liver methionine aminopeptidase

“…Sidorowicz et al, 1981), arginine 2-naphthylamide (Hopsu et al, 1966;Freitas et al, 1979) or leucine 2-naphthylamide (Delange & Smith, 1971). This particular feature of MAP has been shown to be responsible for its higher catalytic efficiency (Vmax /Km) for hydrolysis of methionine 2-naphthylamide compared with other amino acid 2-naphthylamides (Freitas et al, 1985). Furthermore, we found that MAP, in contrast with other wellcharacterized aminopeptidases, is not inhibited by EDTA, puromycin or bestatin (Freitas et al, 1985).…”

“…This particular feature of MAP has been shown to be responsible for its higher catalytic efficiency (Vmax /Km) for hydrolysis of methionine 2-naphthylamide compared with other amino acid 2-naphthylamides (Freitas et al, 1985). Furthermore, we found that MAP, in contrast with other wellcharacterized aminopeptidases, is not inhibited by EDTA, puromycin or bestatin (Freitas et al, 1985). In addition, the lack of EDTA inhibition indicates that MAP is also distinct from all other known metalloaminopeptidases (Barrett, 1977).…”

“…Thus clear evidence for the presence of such an enzyme and of its characterization have not been provided so far, although its existence is widely accepted. We have previously shown that rat liver subcellular fractions contain a typical methionine aminopeptidase distinct from previously described arylaminopeptidases (Freitas et al, 1981(Freitas et al, , 1985. In the present work we have further studied the properties of this aminopeptidase, with special reference to its ability to hydrolyse substrates containing N-terminal methionine in amino acid derivatives as well as peptides, including haemoglobin nascent peptides.…”

“…The active fractions obtained at the non-retained protein peak were combined and concentrated by pressure dialysis and gel-filtered on a 2.6 cm x 92 cm Bio-Gel A-0.5 m column equilibrated and percolated with 20 mM-sodium phosphate buffer, pH 7.0, containing 1.0 mM-2mercaptoethanol. The active fractions were pooled and used as MAP (Freitas et al, 1985).…”

Use of azidobestatin as a photoaffinity label to identify the active site peptide of leucine aminopeptidase

“…Since its discovery in 1976 there have been over 200 publications which relate bestatin and physiological functions, usually via aminopeptidase activity. The following aminopeptidases are inhibited by bestatin: Arg (McDermott et al, 1988), M (Ward et al, 1990;Rich et al, 1984), B (Nishizawa et al, 1977;Harbeson & Rich, 1988), W (Gee & Kenny, 1987), cell surface AP (Aoyagi et al, 1976), AP from erythrocytes (Abramic & Vitale, 1989), AP from cornea (Sharma & Ortwerth, 1987), AP from Aeromonas (Wilkes & Prescott, 1985), and lens AP III (Sharma & Ortwerth, 1986) , but not Met AP (Freitas et al, 1985) or Xanthomonas AP (Osada & Isono, 1986). Bestatin inhibits degradation of endogenous liver proteins (Botbol & Scornik, 1991), enkephalin [most recently treated in Suh andTseng (1990) andBenter et al (1990)], vasopressin (Johnson et al, 1984), melanotropin (Hui et al, 1983), bradykinin (Proud et al, 1987) , angiotensin (Abhold et al, 1987), leukotriene (Hui et al, 1983), and a-bag cell peptide (Squire, et al, 1991).…”