稳定状态的动力学证据表明,果糖-1,6-(二) 酸盐阿尔多酶具有环开放活性
1Biology Department, Boston University, Boston, Massachusetts 02215, USA.
Journal of the American Chemical Society
|March 18, 2004
概括
果糖1,6-双酸盐阿尔多酶 (阿尔多酶) 酶动力学揭示它催化了黑色素环开放. 这表明了潜在的第二个活性部位,挑战了以前对糖解路径的理解.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 代谢途径 代谢途径
背景情况:
- 果糖1,6-双酸盐阿尔多酶是一种关键的糖解酶.
- 一类的阿尔多拉酶需要开放链形式的黑色素基质,以形成希夫基中间体.
- 开放链形式代表了糖在平衡状态中的很小一部分,其与阿尔多酶的结合尚未完全理解.
研究的目的:
- 为了确定与阿尔多酶结合的果糖1,6-双酸盐的化学形式.
- 阐明阿尔多酶催化循环的初始步骤,包括基质结合和希夫基形成.
- 调查阿尔多酶在催化其色基质环开放中的作用.
主要方法:
- 过渡状态动力学使用单次转换实验与过多的阿尔多酶.
- 从初始结合到希夫基形成的反应速率的测量.
- 接近平衡的实验来分析基质结合和反应动力学.
主要成果:
- 希夫基形成速率超过了4°C的α-或β- furanose未催化环开放速率.
- 对于果糖1,6-双酸盐的不同异常物,阿尔多酶表现出不同的结合和反应速率.
- 快速反应阶段 (70%的基质) 与β-anomer相关,缓慢反应阶段 (30%) 与α-anomer相关.
结论:
- 阿尔多酶积极催化果糖1,6-双酸盐的环开放.
- 该酶与不同异常物的相互作用表明特定的基质识别和催化.
- 有证据表明,阿尔多酶上有一个潜在的,以前未被识别的第二个活性位点,用于催化环开放.
相关概念视频
03:05Acid Strength and Molecular Structure
Binary Acids and Bases
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
02:34Molecular Structure and Acidity
An acid can be deprotonated to form a conjugate base or an anion. If the produced anion is more stable, then the acid is stronger. On the contrary, if the anion is unstable, then the acid is weaker. Hence, to determine the acidity of the compound, the stability of its conjugate base is studied using various factors.
The size effect explains the change in atomic size on acidity. When comparing the acids formed from elements that belong to the same column in the periodic table, their atomic sizes...
The size effect explains the change in atomic size on acidity. When comparing the acids formed from elements that belong to the same column in the periodic table, their atomic sizes...
01:31ATP Energy Storage and Release
ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP and inorganic phosphate (Pi), and the free energy released during this process is lost as heat. The energy released by ATP hydrolysis is used to perform work inside the cell and depends on a strategy called energy coupling. Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions, allowing them to proceed.
One example of energy coupling using ATP involves a...
One example of energy coupling using ATP involves a...
01:19Allosteric Proteins-ATCase
Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...