Abstract
The initial rate constants of hydrolysis of 4-nitrophenyl acetate, catalyzed by bile-salt-stimulated human milk lipase, have been measured over the tempera ture range 20 ° C to 37 ° C, in 0.1 M buffer solutions in the pH range 6-10, and in the presence of 2 mM sodium taurocholate. From these data, the values of the energy of activation have been calculated and found to be independent of pH. Analysis of the data has also led to determination of the values of the disso ciation constants, pK1 (8.20) and pK2 (8.70) (at 25°C), and heats of formation, ΔH° (40.2 and 59.4 kJ mol -1, respectively), of the essential ionizable residues of the enzyme.
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References
1.
O'Connor, C.J.
and
J.R. Longbottom.
J. Colloid Interface Sci. , 112 :504 (1986 ).
2.
Hernell, O.
and
T. Olivecrona.
J. Lipid Res ., 15 :367 (1974 ).
3.
O'Connor, C.J.
and
R.G. Wallace.
Adv. Colloid Interface Sci. , 22 :1 ( 1985 ) and refs. cited therein.
4.
Olivecrona, T.
and
O. Hemell.
Pädiatr. Pädol. , 11 :60 ( 1975 ).
5.
O'Connor, C.J.
,
J.R. Longbottom
and
P. Walde.
J. Pediatr. Gastroenterol. Nutr. , 5 :630 ( 1986 ).
6.
O'Connor, C.J.
,
A.S.H. Mitha
and
P. Walde.
Aust. J. Chem. , 39 :249 (1986 ).
7.
Bläckberg, L.
and
O. Hernell.
Eur. J. Biochem. , 116 :221 (1981 ).
8.
Eyring, H.
J Chem. Phys. , 3 :107 (1935 ).
9.
Dixon, M.
Biochem. J , 55 :161 (1953 ).
10.
Edsall, J.T.
, in Proteins, Amino Acids and Peptides .
E. J. Cohn
and
J. T. Edsall
, eds. New York : Reinhold Publishing Corp. (1943 ).
11.
Hernell, O.
and
T. Olivecrona.
Biochim. Biophys. Acta. , 369 :234 (1974 ).
12.
Macey, R.I.
, in Membrane Transport in Biology , Vol. II.
G. Grebisch
,
P. Toteson
, and
H. Ussing
, eds. Berlin :Springer Verlag ( 1979 ).
13.
Sanderman, H.
Biochim. Biophys. Acta. , 515 :209 (1978 ).
14.
Lenaz, G.
Subcell. Biol. , 6 :233 (1980 ).
15.
Macris, B.J.
and
P. Markakis.
J. Sci. Food Agric , 25 :25 ( 1974 ).
16.
McMurchie, E.J.
and
J.K. Raison.
Biochim. Biophys. Acta. , 554 :364 (1974 ).
17.
Wiggins, P.M.
and
R.T. Van Ryn.
J. Macromol. Sci.-Chem. , A23 :875 (1986 ).
18.
Wiggins, P.M.
and
B.A.E. MacClement.
International Reviews in Cytology , 108 , in press ( 1988 ).
19.
Wang, C.-S.
J. Biol. Chem. , 256 :10198 (1981 ).