Dahlquist and coworkers alternatively proposed that beta-glucosidase and this other enzyme catalyzed reactions by covalent substitution, as evidenced from secondary kinetic isotope effects. For 10 points each:
[10m] Name this enzyme, whose rate-determining step is the formation of an oxo-carbenium intermediate in the Phillips mechanism. Hen egg whites are rich in this enzyme, which digests microbial peptidoglycans.
ANSWER: lysozyme [accept muramidase or N-acetylmuramide glycanhydrolase]
[10h] Several Bacillus enzymes remove this chemical group from glucosamine and muramic acid to confer resistance to lysozyme. This group is added to lysine residues by the eukaryotic p300/CBP and MYST family of proteins.
ANSWER: acetyl groups [accept N-acetyl groups; accept -COCH3 or -CH3CO; prompt on acyl groups; prompt on carbonyl groups]
[10e] Lysozymes also have limited cross-reactivity against this compound, which is hydrolyzed by a “human” enzyme often linked to household allergies. Arthropod exoskeletons are primarily composed of this compound.
ANSWER: chitin
<AL, Chemistry>