Chapter 32: Problem 747
Explain how the conjugate base of thiamine might react with pyruvic acid to produce an intermediate which could easily decarboxylate. Complete the reaction sequence leading to the formation of acetoin.
Chapter 32: Problem 747
Explain how the conjugate base of thiamine might react with pyruvic acid to produce an intermediate which could easily decarboxylate. Complete the reaction sequence leading to the formation of acetoin.
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Get started for freeThe proteolytic enzyme, papain, differs from \(\alpha\) -chymdtrypsin in having cysteine or a labile derivative thereof as part of its active site. The enzyme is deactivated by substances that form complexes with, or react with, -SH groups and the activity is restored by reactions expected to regenerate an -SH group. Work out a schematic mechanism for cleavage of a peptide chain with papain which is in agreement with the idea that, while papain may not normally contain a free \(\mathrm{SH}\) group, it reacts readily with mercuric ion to give compounds of the type RSHgX. One of the most interesting features of papain is that more than 100 of its total of 185 amino acid residues may be removed with the aid of an aminopeptidase to give a fragment with considerable enzymic activity.
Hemoglobin, the protein responsible for carrying oxygen from the lungs to the body tissues, contains \(0.355\) per cent iron. Hydrolysis of \(100 \mathrm{~g}\) of hemoglobin gives \(1.48 \mathrm{~g}\) of tryptphan; calculate the minimum molecular weight of hemoglobin which is consistent with these results.
Many years before the Hofmann degradation of optically active a-phenylpropionamide was studied, the following observations were made: when the cyclopentane derivative, \(\mathrm{I}\), in which the \(-\mathrm{COOH}\) and \(-\mathrm{CONH}_{2}\) groups are cis to each other, was treated with hypobromite, compound II was obtained; compound II could be converted by heat into the amide III (called a lactam). What do these results show about the mechanism of the rearrangement? (Use models.)
Show how the following amino acids can be prepared from the indicated starting materials. (a) leucine from isobuty1 alcohol (b) lysine from 1,4 -dibromobutane (c) proline from adipic acid (d) glutamic acid from \(\alpha\) -ketoglutaric acid
Suggest a way to separate a mixture of amino acids into three fractions: monoamino monocarboxylic acids, monoamino dicarboxylic acids (the acidic amino acids), and diamino monocarboxylic acids (the basic amino acids).
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