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Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase.
Indian J Biochem Biophys. 1991 Oct-Dec; 28(5-6):381-8.IJ

Abstract

The mechanism of interaction of methoxyamine with sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) (SHMT) was established by measuring changes in enzyme activity, visible absorption spectra, circular dichroism and fluorescence, and by evaluating the rate constant by stopped-flow spectrophotometry. Methoxyamine can be considered as the smallest substituted aminooxy derivative of hydroxylamine. It was a reversible noncompetitive inhibitor (Ki = 25 microM) of SHMT similar to O-amino-D-serine. Like in the interaction of O-amino-D-serine and aminooxyacetic acid, the first step in the reaction was very fast. This was evident by the rapid disappearance of the enzyme-Schiff base absorbance at 425 nm with a rate constant of 1.3 x 10(3) M-1 sec-1 and CD intensity at 430 nm. Concomitantly, there was an increase in absorbance at 388 nm (intermediate I). The next step in the reaction was the unimolecular conversion (1.1 x 10(-3) sec-1) of this intermediate to the final oxime absorbing at 325 nm. The identity of the oxime was established by its characteristic fluorescence emission at 460 nm when excited at 360 nm and by high performance liquid chromatography. These results highlight the specificity in interactions of aminooxy compounds with sheep liver serine hydroxymethyltransferase and that the carboxyl group of the inhibitors enhances the rate of the initial interaction with the enzyme.

Authors+Show Affiliations

Department of Biochemistry, Indian Institute of Science, Bangalore.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

1812071

Citation

Acharya, J K., et al. "Interactions of Methoxyamine With pyridoxal-5'-phosphate-Schiff's Base at the Active Site of Sheep Liver Serine Hydroxymethyltransferase." Indian Journal of Biochemistry & Biophysics, vol. 28, no. 5-6, 1991, pp. 381-8.
Acharya JK, Prakash V, Rao AG, et al. Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase. Indian J Biochem Biophys. 1991;28(5-6):381-8.
Acharya, J. K., Prakash, V., Rao, A. G., Savithri, H. S., & Rao, N. A. (1991). Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase. Indian Journal of Biochemistry & Biophysics, 28(5-6), 381-8.
Acharya JK, et al. Interactions of Methoxyamine With pyridoxal-5'-phosphate-Schiff's Base at the Active Site of Sheep Liver Serine Hydroxymethyltransferase. Indian J Biochem Biophys. 1991 Oct-Dec;28(5-6):381-8. PubMed PMID: 1812071.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase. AU - Acharya,J K, AU - Prakash,V, AU - Rao,A G, AU - Savithri,H S, AU - Rao,N A, PY - 1991/10/1/pubmed PY - 1991/10/1/medline PY - 1991/10/1/entrez SP - 381 EP - 8 JF - Indian journal of biochemistry & biophysics JO - Indian J. Biochem. Biophys. VL - 28 IS - 5-6 N2 - The mechanism of interaction of methoxyamine with sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) (SHMT) was established by measuring changes in enzyme activity, visible absorption spectra, circular dichroism and fluorescence, and by evaluating the rate constant by stopped-flow spectrophotometry. Methoxyamine can be considered as the smallest substituted aminooxy derivative of hydroxylamine. It was a reversible noncompetitive inhibitor (Ki = 25 microM) of SHMT similar to O-amino-D-serine. Like in the interaction of O-amino-D-serine and aminooxyacetic acid, the first step in the reaction was very fast. This was evident by the rapid disappearance of the enzyme-Schiff base absorbance at 425 nm with a rate constant of 1.3 x 10(3) M-1 sec-1 and CD intensity at 430 nm. Concomitantly, there was an increase in absorbance at 388 nm (intermediate I). The next step in the reaction was the unimolecular conversion (1.1 x 10(-3) sec-1) of this intermediate to the final oxime absorbing at 325 nm. The identity of the oxime was established by its characteristic fluorescence emission at 460 nm when excited at 360 nm and by high performance liquid chromatography. These results highlight the specificity in interactions of aminooxy compounds with sheep liver serine hydroxymethyltransferase and that the carboxyl group of the inhibitors enhances the rate of the initial interaction with the enzyme. SN - 0301-1208 UR - https://www.unboundmedicine.com/medline/citation/1812071/Interactions_of_methoxyamine_with_pyridoxal_5'_phosphate_Schiff's_base_at_the_active_site_of_sheep_liver_serine_hydroxymethyltransferase_ DB - PRIME DP - Unbound Medicine ER -