Stereochemical course of the reaction catalyzed by the pyridoxal phosphate-dependent enzyme 1-aminocyclopropane-1-carboxylate synthase
(+/-)-S-adenosyl-DL-(3R*,4S*)-(3,4-/sup 2/H/sub 2/)-methionine(a 1:1 mixture of (3R,4S) and (3S,4R) and (+/-)-S-adenosyl-DL-(3R*,4R*)-(3,4-/sup 2/H/sub 2/)methionine (a 1:1 mixture of (3R,4R) and (3S,4S)) were synthesized from (Z)- and (E)-(1,2-/sup 2/H/sub 2/)ethene, respectively. Key steps in the synthesis were the antiperiplanar addition of methanesulfenyl chloride to (Z)-(1,2-/sup 2/H/sub 2/)ethene, to give a 1:1 mixture of (R,R)- and (S,S)-1-chloro-2-(methylthio)(1,2-/sup 2/H/sub 2/)ethane, followed by alkylation with soldium acetamidomalonate and hydrolysis to give an equal mixture of four stereoisomers of (3,4-/sup 2/H/sub 2/)methionine ((2R,3R,4S), (2R,3S,4R), (2S,3R,4S), and (2S,3S,4R)). The other four stereoisomers of (3,4-/sup 2/H/sub 2/)methionine were prepared from (E)-(1,2-/sup 2/H/sub 2/)ethene. The two sets of stereoisomers of (3,4-/sup 2/H/sub 2/)methionine were chemically converted to S-adenosylhomocysteine, methylated to give the corresponding (+/-)-S-adenosyl-DL-methionines, and then incubated with 1-aminocyclopropane-1-carboxylate synthase partially purified from tomato (Lycopersicon esculentum, L.)pericarp tissue. The stereochemistry of the resulting samples of 1-aminocyclopropane-1-carboxylic acid was determined by comparison with the /sup 1/H NMR of the chemically synthesized and regio- and stereo-specifically deuterated compound. The results indicate that the hydrogens at the ..beta.. carbon of the methionine portion of S-adenosylmethionine do not participate in the reaction and that the ring closure occurs with inversion of configuration at the ..gamma.. carbon of the methionine portion of S-adenosyl-methionine, probably through a direct S/sub N/2-type displacement of the 5'-methylthio-5'-deoxyadenosine moiety by a carbanion equivalent formed at the ..cap alpha.. carbon of the methionine portion of S-adenosylmethionine.
- Research Organization:
- Univ. of Michigan, Ann Arbor
- DOE Contract Number:
- AC02-76ER01338
- OSTI ID:
- 6194523
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 82:23; ISSN PNASA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALKYLATION
AMINO ACIDS
CARBOXYLIC ACIDS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DEUTERIUM
DRUGS
ENZYME ACTIVITY
ENZYMES
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGASES
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
METHIONINE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RESONANCE
STABLE ISOTOPES
STEREOCHEMISTRY
SYNTHESIS
TRACER TECHNIQUES