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Pseudo-enzymatic Hydrolysis of 4-nitrophenyl Myristate by Human Serum Albumin

Pseudo-enzymatic Hydrolysis of 4-nitrophenyl Myristate by Human Serum Albumin

Paolo Ascenzi, Mauro Fasano

Biochem Biophys Res Commun. 2012 Jun 1;422(2):219-23.

PMID: 22560903

Abstract:

Most of the esterase properties of human serum albumin (HSA) are the result of multiple irreversible chemical modifications rather than turnover. The HSA-catalyzed hydrolysis of 4-nitrophenyl myristate (NphOMy) is consistent with the minimum three-step mechanism involving the acyl-enzyme intermediate HSA-OMy: Under all the experimental conditions, values of K(s) (= k(-1)/k(+1)), k(+2), and k(+2)/K(s) determined under conditions where [HSA] ≥ 5 × [NphOMy] and [NphOMy] ≥ 5 × [HSA] match very well each other. The deacylation process is rate limiting in catalysis (i.e., k(+3) << k(+2)) and k(-2)~k(-3)~0 s(-1). The pH dependence of k(+2)/K(s), k(+2), and K(s) reflects the acidic pK(a)-shift of one ionizing group from 8.9 ± 0.2 in NphOMy-free HSA to 6.8 ± 0.3 in the HSA:NphOMy adduct. The HSA-catalyzed hydrolysis of NphOMy is inhibited competitively by diazepam, indicating that Tyr411 is the active-site nucleophile.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP14617857	4-Nitrophenyl myristate		14617-85-7	Price

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