Abstract:
:Previous work has shown that catalytic function is associated exclusively with the C-terminal half of the Type I isozyme of mammalian hexokinase. In contrast, we now demonstrate that both halves of the Type II isozyme possess comparable catalytic activities. Mutation of a catalytically important Ser residue to Ala at analogous positions in either the N- or the C-terminal halves (S155A or S603A, respectively) of the rat Type II isozyme resulted in approximately 60% reduction in specific activity of the enzyme, with more than 90% reduction in the doubly mutated enzyme (S155A/S603A). Catalytic activity was retained in a chimeric hexokinase comprising the N-terminal half of Type II hexokinase and catalytically inactive (by site-directed mutation) C-terminal half of the Type I isozyme. The N- and C-terminal catalytic sites of Type II hexokinase are similar in V(max) and K(m) (approximately equal to 130 microM) for glucose; however, the N-terminal site has a lower (0.45 vs 1.1 mM) K(m) for ATP, is slightly more sensitive to inhibition by the product analog 1,5-anhydroglucitol-6-P, and is much more sensitive to inhibition by P(i). It is suggested that the Type II isozyme most closely resembles the 100-kDa hexokinase which resulted from duplication and fusion of a gene encoding an ancestral 50-kDa hexokinase and which was the precursor for the contemporary Type I, Type II, and Type III mammalian isozymes. Subsequent evolutionary changes could then have led to functional differentiation of the N- and C-terminal halves, as seen with the Type I (and possibly the Type III) isozyme.
journal_name
Arch Biochem Biophysjournal_title
Archives of biochemistry and biophysicsauthors
Tsai HJ,Wilson JEdoi
10.1006/abbi.1996.0186subject
Has Abstractpub_date
1996-05-01 00:00:00pages
17-23issue
1eissn
0003-9861issn
1096-0384pii
S0003-9861(96)90186-1journal_volume
329pub_type
杂志文章abstract::The spectral properties of 4-methylumbelliferyl-glycosides (MeUmb-glycosides) were investigated in order to assess their usefulness as probes of the microenvironment of sugar binding sites on lectin molecules. It was shown that the abnormally high values for fluorescence polarization of free MeUmb-glycosides (from 0.0...
journal_title:Archives of biochemistry and biophysics
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doi:10.1016/0003-9861(84)90584-8
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abstract::Dethiolation of proteins (reduction of protein mixed disulfides) by NADPH-dependent and glutathione (GSH)-dependent enzymes, and by nonenzymatic reaction with GSH, was studied by electrofocusing methodology with glycogen phosphorylase b and creatine kinase as substrates. Phosphorylase b was not rapidly dethiolated by ...
journal_title:Archives of biochemistry and biophysics
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doi:10.1016/0003-9861(89)90413-x
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1006/abbi.2000.2141
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1016/0003-9861(90)90501-o
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1006/abbi.1999.1505
更新日期:1999-12-15 00:00:00
abstract::Cytosolic extracts from the posterior adductor muscle of the bivalve mollusk Mytilus galloprovincialis contain significant amounts of both cGMP-binding and cGMP-stimulated protein kinase activities. However, photoaffinity labeling with 8-azido-[32P]cGMP revealed only a major cGMP-binding protein with an apparent molec...
journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1006/abbi.1998.0879
更新日期:1998-11-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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更新日期:2012-02-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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pub_type: 杂志文章
doi:10.1006/abbi.1996.0185
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pub_type: 杂志文章
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更新日期:1998-04-01 00:00:00
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pub_type: 杂志文章
doi:10.1006/abbi.1993.1098
更新日期:1993-02-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1016/0003-9861(89)90180-x
更新日期:1989-08-15 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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journal_title:Archives of biochemistry and biophysics
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更新日期:1993-02-15 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1006/abbi.2000.2004
更新日期:2000-11-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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更新日期:2010-12-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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更新日期:1988-11-15 00:00:00
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
doi:10.1006/abbi.1994.1415
更新日期:1994-10-01 00:00:00
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journal_title:Archives of biochemistry and biophysics
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更新日期:2015-10-01 00:00:00
abstract::A gold(III) compound [Au(C^N^C)(IMe)]CF(3)SO(3) (Gold III) has been reported to have anticancer properties as it is able to reduce topoisomerase IB activity in vitro and suppress tumor growth in nude mice model. Here we have investigated the mechanism of inhibition of human topoisomerase IB activity by this compound, ...
journal_title:Archives of biochemistry and biophysics
pub_type: 杂志文章
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更新日期:2011-12-15 00:00:00