Feedback inhibition by methionine and S-adenosylmethionine, and desensitization of homoserine O-acetyltransferase in Brevibacterium flavum.
-
- SHIIO Isamu
- Central Research Laboratories, Ajinomoto Co., Inc.
-
- OZAKI Hachiro
- Central Research Laboratories, Ajinomoto Co., Inc.
抄録
Homoserine O-acetyltransferase [EC 2. 3. 1. 31] partially purified from Brevibacterium flavum was found to be specifically inhibited by the metabolic end products methionine and S-adenosylmethionine only when the enzymatic reaction was performed in the presence of cysteine or dithiothreitol, or after the preincubation of the enzyme with either of the sulfhydryl compounds. p-Hydroxymercuribenzoate desensitized the enzyme to inhibition. Concentrations of methionine and S-adenosylmethionine giving 50% inhibition were 4.8 and 0.26mM, respectively, and 0.5mM S-adenosylmethionine showed almost complete inhibition. No synergistic action by the two inhibitors was found. Optimum pHs were 7.5 and 8.5 for the inhibition by methionine and S-adenosylmethionine, respectively. The inhibitions by the former and the latter were of mixed type and non-competitive respectively, with respect to both substrates, homoserine and acetyl-CoA. Plots of the reaction rate against concentration of the inhibitors were sigmoidal, indicating the presence of co-operativity. N-Formylmethionine, α-methylmethionine, trifluoromethionine, selenomethionine, ethionine or S-adenosylhomocysteine inhibited the enzyme to almost the same extent as methionine or S-adenosylmethionine. The enzyme irreversibly lost sensitivity to inhibition during extraction or storage. Sensitivity was retained by the addition of cysteine, dithiothreitol, homoserine (substate), or glycerol.
収録刊行物
-
- The Journal of Biochemistry
-
The Journal of Biochemistry 89 (5), 1493-1500, 1981
The Japanese Biochemical Society
- Tweet
詳細情報 詳細情報について
-
- CRID
- 1571980078017603328
-
- NII論文ID
- 130003541734
-
- ISSN
- 0021924X
-
- 本文言語コード
- en
-
- データソース種別
-
- CiNii Articles