There is also an ornithine transporter that transport ornithine from the cytosol into the matrix of the mitochondria. The rest of the reactions of the urea cycle occur in the cytosol. Second Step: The next step of the urea cycle is catalyzed by argininosuccinate synthetase. This enzyme uses ATP to activate citrulline by forming a citrully-AMP intermediate. In the second half of the argininosuccinate synthetase reaction, the α-amino group of aspartate attacks the imino carbon releasing AMP and producing argininosuccinate.
3.Mechanism of threonine protease Threonine proteases use the secondary alcohol of their N-terminal threonine as a nucleophile to perform catalysis. ( Brannigan,etal1995) The threonine must be N-terminal since the terminal amine of the same residue acts as a general base by polarising an ordered water which deprotonates the alcohol to increase its reactivity as a nucleophile. ( Ekici, OD 2008) Catalysis takes place in two
ADH assay was carried out to oxidise the ethanol to acetaldehyde and two marker enzymes G6PDH and ALP assays were carried out to aid in the determination of the localisation on YAD. It is concluded that conclude that the ADH enzyme of yeast Saccharomyces cerevisiae that concentrated in the supernatant fraction is located in the cytosol of
Squalene undergoes a two-step cyclization to yield lanosterol catalyzed by sequalene mono-oxygenase and sequalene 2, 3 epoxidase enzymes. Sequalene mono oxygenase is the second committed step in cholesterol biosynthesis and lead to the formation squalene 2, 3 epoxide. This enzymatic reaction require supernatant protein factor (SPF) and NADPH as a cofactor to introduce molecular oxygen as an epoxide at the 2, 3 position of squalene. The activity of supernatant protein factor itself is regulated by phosphorylation/dephosphorylation (Singh et al., 2003). Through a series of 19 additiona lreactions, lanosterol is converted to cholesterol.
Malate dehydrogenase: Malate dehydrogenase (MDH) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxaloacetate by using NAD+ and vice versa and this is a reversible reaction. Malate dehydrogenase is not to be confused with malic enzyme, both are different enzymes malic enzyme which catalyzes the conversion of malate to pyruvate and producing NADPH. Malate dehydrogenase is also involved in gluconeogenesis, in which the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is based upon pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. The malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane to get the oxaloacetate out
The products of this stage are passed down into the next stages. The 2 molecules of pyruvate are passed down to the oxidation of pyruvate, and NADH will be used for the electron transport chain. The rest of the products, 4 ATP, ADP, and P, are used where needed in the cell. After glycolysis occurs, oxidation of pyruvate takes places in the mitochondrial matrix. During this stage,
An enzyme is a biomolecule that acts as a catalyst in biochemical reactions (1). Enzymes are commonly used in many products and medications. Enzymes function by flexibly binding to active sites in substrates (reactants). This binding is weak non-covalent interactions. The Michaelis Menten model is used to show the relationship between velocity and substrate concentration, such as in figures four and five.
Regeneration of the catalytically active coenzymes occur either in the same reaction or in subsequent metabolic reaction. A complete catalytically active enzyme together with its coenzyme or cofactor is called holoenzyme, where as protein part is known as
Introduction: L-Asparaginase (L-asparagine amido-hydrolase; EC 220.127.116.11), belongs to the amidohydrolase family. It catalyzes the breakdown of L-asparagine to ammonia and L-aspartic acid. The ammonia produced can be quantified using a gas analyzer with ammonia sensing electrodes (Fraticelli and Meyerhoff, 1983) or the ammonia can be combined with α-ketogluterate to form L-glutamic acid using glutamate dehydrogenase. This reaction is marked with a decline in the NADH concentrationand is detected as a loss of absorbance at 340 nm. Thus the activity of L-Asparaginase can be determined and expressed as ASNU unites where one ASNU is defined as "The amount of L-Asparaginase that produces 1 micromole ammonia per minute under the conditions of the assay (pH=7±0.05;temperature= 37.0 ±0.5 ºC) (Pronk et al., 2008).