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His-163 is a stereospecific proton donor in the mechanism of d-glucosaminate-6-phosphate ammonia-lyase.

ABSTRACT: d-Glucosaminate-6-phosphate ammonia-lyase (DGL) catalyzes the conversion of d-glucosaminate-6-phosphate to 2-keto-3-deoxyglutarate-6-phosphate, with stereospecific protonation of C-3 of the product. The crystal structure of DGL showed that His-163 could serve as the proton donor. H163A mutant DGL is fully active in the steady-state reaction, and the pre-steady-state kinetics are very similar to those of wild-type DGL. However, H163A DGL accumulates a transient intermediate with λ_max at 293 nm during the reaction that is not seen with wild-type DGL. Furthermore, NMR analysis of the reaction of H163A DGL in D₂ O shows that the product is a mixture of deuterated diastereomers at C-3. These results establish that His-163 is the proton donor in the reaction mechanism of DGL.

SUBMITTER: Phillips RS

PROVIDER: S-EPMC9529869 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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His-163 is a stereospecific proton donor in the mechanism of d-glucosaminate-6-phosphate ammonia-lyase.

Phillips Robert S RS Anderson Kaitlin L KL Gresham Declan D

FEBS letters 20220829 18

d-Glucosaminate-6-phosphate ammonia-lyase (DGL) catalyzes the conversion of d-glucosaminate-6-phosphate to 2-keto-3-deoxyglutarate-6-phosphate, with stereospecific protonation of C-3 of the product. The crystal structure of DGL showed that His-163 could serve as the proton donor. H163A mutant DGL is fully active in the steady-state reaction, and the pre-steady-state kinetics are very similar to those of wild-type DGL. However, H163A DGL accumulates a transient intermediate with λ<sub>max</sub> a ...[more]

PMID: 35953460

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