Biochemistry Answers

Both ALDH1 (in cytoplasm) and ALDH2 (in mitochondria) can covert aldehyde to acetate but with different values of Km. According to (Harada et al, 1980), at pH9.5, ALDH1 has Km of 0.1 – 0.4 mM and ALDH2 has Km of 0.01 – 0.02 mM. Which has a higher affinity, and why?

What is pI? How the knowledge of the pI of a protein enables characterisation of the protein?

In an enzymatic reaction, after adding an inhibitor, the observed Vmax was reduced but the Km value was unchanged. What type of inhibition occurred to this enzymatic reaction?

Inhibitors are often used to reduce activities of an enzyme in clinical treatment. If you need to choose an inhibitor that only affects the substrate binding site of an enzyme, how would you find out if the inhibitor could do the specific “job”?

Both ALDH1 (in cytoplasm) and ALDH2 (in mitochondria) can covert aldehyde to acetate but with different values of Km. According to (Harada et al, 1980), at pH9.5, ALDH1 has Km of 0.1 – 0.4 mM and ALDH2 has Km of 0.01 – 0.02 mM. Which has a higher affinity, and why?

A molecular biologist sequenced a partial human DNA fragment and find it shares 98% identity with first half (5’ end) of a mouse gene in which the second half (3’ end) has a restriction site (AAGCTT) for endonuclease HindIII (i.e. Hind III can cut this DNA into two parts at this place). Without sequencing the rest of the human gene, he decided to examine it with HindIII digestion. The result of the digestion did not yield expected restriction fragments as revealed by agarose gel electrophoresis. Please list

Aldehyde dehydrogenase (ALDH) catalyses the conversion of aldehyde to acetate. Please explain how the change of the cycteine to tyrosin in position 19 of ALDH causes the loss of the function of ALDH.

A weak acid at pH6 medium, when 91% of it becomes neutralized, what is its pKa (please show steps of the calculation)?