THE ACTIVE-SITE OF VITAMIN-K AND THE ROLE OF THE VITAMIN-K-DEPENDENT CARBOXYLASE
- Authors
- NAGANATHAN, S; HERSHLINE, R; HAM, SW; DOWD, P
- Issue Date
- Nov-1994
- Publisher
- AMER CHEMICAL SOC
- Citation
- JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.116, no.22, pp 9831 - 9839
- Pages
- 9
- Journal Title
- JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
- Volume
- 116
- Number
- 22
- Start Page
- 9831
- End Page
- 9839
- URI
- https://scholarworks.bwise.kr/cau/handle/2019.sw.cau/56037
- DOI
- 10.1021/ja00101a003
- ISSN
- 0002-7863
1520-5126
- Abstract
- Vitamin K is the blood-clotting vitamin. It participates in the blood coagulation cascade as a carboxylase cofactor. Enzymic oxygenation of vitamin K hydroquinone provides the driving force for the carboxylation of selected glutamates in the proteins of the blood-clotting cascade. The active site of vitamin K has now been defined by O-18-labeling experiments. The oxygenation is completely specific for the carbonyl group adjacent to the quinone methyl group of vitamin K. The experiment makes use of the O-18-labeled vitamin K isotopomers 9 and 10. Thus, oxygenation of 9 with O-16(2) occurs at the carbonyl group next to methyl, as shown by exchange of the O-18 label at that position. Synthesis of the two O-18-labeled vitamin K isotopomers 9 and 10 was accomplished by cerium(IV)-mediated oxidation in the presence of (H2O)-O-18 of the corresponding methyl half-ethers 4 and 8. The position of the label was ascertained by C-13 and heteronuclear NOE NMR spectroscopies. A role for the active site thiols on the vitamin K-dependent carboxylase is also suggested. The thiolate anion is an excellent candidate for the weak base that initiates the base strength amplification sequence leading to carboxylation and vitamin K oxide formation.
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