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, MI (United States)
- DOE Contract Number:
- AC02-76ER01338
- OSTI ID:
- 6194523
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 82:23
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LIGASES
ENZYME ACTIVITY
METHIONINE
CHEMICAL PREPARATION
ALKYLATION
CARBOXYLIC ACIDS
DEUTERIUM
LABELLED COMPOUNDS
NUCLEAR MAGNETIC RESONANCE
STEREOCHEMISTRY
TRACER TECHNIQUES
AMINO ACIDS
CHEMICAL REACTIONS
DRUGS
ENZYMES
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RESONANCE
STABLE ISOTOPES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques