@article{oai:ir.kagoshima-u.ac.jp:00011029,
 author = {大城, 善太郎},
 issue = {2},
 journal = {鹿児島大学水産学部紀要=Memoirs of Faculty of Fisheries Kagoshima University},
 month = {2016-10-31},
 note = {It was, at the outset, demonstrated that the precipitate yielded abundantly on the
dialysis of a saline extract of the pyloric coeca of mackerel, Scomber japonicus, showed an enzymatic activity which catalyses both the hydrolysis of chloroacetyl-L-tyrosine and the asymmetric hydrolysis of chloroacetyl-DL-phenylalanine. The active
enzymatic principle was assumed to be a carboxypeptidase (CPase).
Zone electrophoresis indicated that a major constituent of the precipitate was
repsonsible for the enzyme activity. The active priciple was separated through a
well arranged employment of the DEAE-cellulose column chromatography, and an
ultracentrifugally homogenous CPase was isolated. The chromatogram obtained
through this procedure was found to be quite different from that obtained from the bovine pancreatic CPase under the same
experimental conditions., By the purification procedure, the specific activity of the enzyme was increased as much as 4.3 times. A sedimentation constant (st) of 3.25×10^[-13] was obtained by
the ultracentrifugation. The molecular weight was calculated to be 23,500, which was
definitely smaller than that of the bovine pancreatic CPase, 34,000. This fact suggests
that these two forms of CPase consist of different types of proteins.
Optimal pH and temperature for the hydrolysis of carbobenzoxyglycyl-L-phenylalanine were found to be 8.0 and 35-40°C respectively. Furthermore, the mackerel
pyloric coeca CPase was ascertained to be a type of metal enzyme.
Effects of various metals on the activity of this enzyme were examined. No effect was brought about by calcium and magnesium. The activity was inhibited by manganese and zinc as much as 50 per cent, while it was five times activated by cobalt. On the other hand, the activity was arrested by the chelating agent EDTA. The enzyme inactivated in this way was reactivated by calcium, magnesium and, particularly, by cobalt, but not by zinc.
The mackerel pyloric coeca CPase differs also in
this respect from the bovine pancreatic CPases, although the substrate specificities of these two enzymes are identical., Judging from the way of the asymmetric hydrolysis of chloroacetyl-DL-phenylalanine,
chloroacetyl-DL-tyrosine, and chloroacetyl-DL-leucine, the pyloric coeca CPases is
assumed to be a type of CPase-A, although it apparently differs from the bovine
pancreatic CPase-A in the nature of the enzyme protein.
Finally, some physico-chemical properties were investigated on both the intact and the cobalt-treated pyloric coeca CPase. The kinetic constants, such as Michaelis
constant K_m, V_max, activation energies E_A, and the various velocity constants, were
determined in the case of the hydrolysis of carbobenzoxy-glycyl-L-phenylalanine, and these kinetic constants of the two types of the enzyme were studied comparatively
to elucidate the mechanism of the participation of cobalt ion in the activation of the enzyme.
The activation energies, k_1/k_1, and k_2/k_1 decreased by treatment of the enzyme
with cobalt ion, together with the corresponding, directly proportional diminution of
K_m. Judging from these facts, it is postulated that a close combination of cobalt ion
with the active center or the enzyme occurs quite readily to form a favorable structure of the active site and the stable ES-complex.},
 pages = {111--151},
 title = {サバ幽門垂カルボキシペプチダーゼに関する研究},
 volume = {11},
 year = {}
}