Uncoating of clathrin coated vesicles

Because of their clathrin coats, clathrin coated vesicles can not fuse directly with the endosome. And because clathrin coats form spontaneously, energy is required to disassemble them again. This reaction is catalysed by a molecular chaperone, Hsc70 (see page 212), also known as the uncoating ATPase. There is an equilibrium between bound and free clathrin arms. Hsc70-ATP binds to exposed clathrin arms, preventing them from rejoining the coat. This shifts the equilibrium from coat assembly to...

Info

Proteins can be described by a set of concise classification strings (sccs) according to their structure, for example b.2.1.1 (class b all 3, fold 2 NAD(P)+-binding R0SSMANN-fold domains, superfamily 1 Alcohol dehydrogenase-like and family 1 Alcohol dehydrogenase). Within families, proteins are sorted by species and isoform. Protein structures are stored in the Brookhaven Protein Data Bank (PDB) in a unified format that can be used by modelling software like protein explorer index.htm),...

Enzyme classification and EC code

Each cell contains several thousand different enzymes, each a specialist that performs one reaction on one substrate (or at least a small group of similar substrates). Originally each enzyme was given a name by its discoverer, and many such names are still in use today, like trypsin, pepsin or invertase. However, as the number of known enzymes increased, this system became untenable. Today enzymes are named in a systematic way. The name of the substrate is followed by the name of the reaction...

A brief history of enzymology

Most of the topics in this brief overview are covered in more detail in the following chapters. For further reading into enzymology 5, 18, 45 are suggested. If you have to deal with rate equations in special cases 70 is still useful. The properties of catalysts were described by the German-Russian chemist Gottlieb Sigismund Constantin Kirchhoff, who could show in 1812 that the hydrolysis of starch to glucose is accelerated by acid, and that the acid is not used up in the process1. In 1814 he...

[ES Ka [S [E66

Strictly speaking, we would have to use the concentration of free substrate, S , for these calculations. This concentration we do not know however, all we know is the total substrate concentration S t S + ES . However, if S t E t, formation of the ES complex does not appreciably change the concentration of free substrate. In experiments, we can therefore use S t as an approximation for S . This assumption can not be used for the enzyme however. Ka is called association constant for the binding...

The coupled spectrophotometric assay of Warburg

The concentration of substrates and enzymes in clinical samples is often determined using the coupled spectrophotometric assay which was introduced by O. Warburg 80 . Figure 6.18. A) UV-spectra of NAD+ and NADH + H+ (in water). Both have an absorbance maximum at 260 nm, attributable to the adenine-ring. NAD(P)H + H+ has an additional absorbance maximum at 340 nm, which can be used to distinguish it from NAD(P) + . B) Change of UV-absorbance over time during a coupled spectrophotometric test....