Armand J. Fulco

ω-1, ω-2 and ω-3 Hydroxylation of long-chain fatty acids, amides and alcohols by a soluble enzyme system from Bacillus megatyerium

A soluble enzyme preparation from Bacillus megaterium, previously shown to hydroxylate free fatty acids to isomeric mixtures of Omega-1, Omega-2 and Omega-3 monohydroxy fatty acids in the presence of NADPH and O2, has now been shown to act also on fatty amides but not only hydrocarbons or fatty acid methyl esters. Using 14-C-labelled substrates, both the chain-length specificity and the positional specificity of hydroxylation was determined for fatty acids, alcohols and amides. The most active saturated fatty acid (pentadecanoic) was hydroxylated at a rate 10 times greater than the most active amide (myristamide) and 14 times faster than the most active alcohol (1-tetradecanol). Among the saturated fatty acids, the order of activity as hydroxylation substrates was C15 greater than C16 greater than C14 greater than C17 greater than C13 greater than C18 = C12. For amides the order was C14 greater than C12 greater than C15 greater than C16 while for alcohols it was C14 greater than C13 = C15 greater than C12 greater than C15. Four cis-monounsaturated fatty acids were also tested. Oleic, palmitoleic and cis-12-octadecenoic acids were more active than their saturated analogs but cis-5-tetradecenoate was less active than myristate. For all of the substrates mentioned above, with the possible exception of several unsaturated acids, the alkyl chains were monohydroxylated to give isomeric mixtures of the Omega-1, Omega-2 and Omega-3 derivatives. The distribution of these three isomers varied with chain-length and type of substrate but generally, the Omega-2 position was favored. The terminal methyl (Omega) group of these substrates was never hydroxylated and there did not appear to be significant hydroxylation of methylene carbons beyond the Omega-3 position. Based on the data presented here and in a previous paper, a model is proposed for the enzyme-substrate complex which involves hydrophobic binding and sequestering of the terminal methyl group of the substrate and electrostatic binding of the substrates polar functional group.

Characteristics of a cytochrome P-450-dependent fatty acid ω-2 hydroxylase from Bacillus megaterium

The fatty acid (omega-2) hydroxylase from Bacillus megaterium ATCC 14581 was examined with respect to some general enzymatic properties attributed to an intact complex isolated in a partially purified state. Hydroxylase specific activity was found to increase with increasing protein concentration in a manner consistent with a reversible association of the components in the complex. There was a substantial kinetic lag phase for palmitate hydroxylation which was abolished by a substrate preincubation in the absence of NADPH. The substrate bound and presumably activated the hydroxylase complex without the formation of a substrate-derived intermediated. The oxidation of NADPH and the hydroxylation of palmitate were found to occur in a one to one molar ration, independent of the protein concentration. Finally, a cytochrome P-450 component of the complex was identified on the basis of its CO-binding difference spectrum. It appears, that this cytochrome P-450 component is not identical to P-450 meg of the steroid hydroxylase system of B. megaterium ATCC 13368, since progesterone, an active substrate for the latter, is not hydroxylated by the preparation from B. megaterium ATCC 14581.

Involvement of a single hydroxylase species in the hydroxylation of palmitate at the ω—1, ω—2 and ω—3 positions by a preparation from Bacillus megaterium

Abstract A soluble enzyme preparation from Bacillus megaterium , requiring NADPH and O 2 for activity and containing ferredoxin-replaceable and cytochrome P -450- type components, was previously shown to catalyze the conversion of palmitic acid to an isomeric mixture of ω—1, ω—2 and ω—3 hydroxypalmitate. It has now been shown that the ratio of these three positional isomers in the enzymatic product remains unchanged in spite of partial diminution of total hydroxylase activity by heat treatment, pH change or inhibition by p -hydroxymercuribenzoate or carbon monoxide. These findings strongly support the hypothesis that a single hydroxylase with one substrate binding site is responsible for hydroxylation at all three positions of palmitate.

Induction by barbiturates of a cytochrome P-450-dependent fatty acid monooxygenase in Bacillus Megaterium: Relationship between barbiturate structure and inducer activity

In a recent communication (Narhi, L. and Fulco, A.J. [1982] J. Biol. Chem. 257, 2147-2150) we found that a soluble cytochrome P-450-dependent fatty acid monooxygenase isolated from Bacillus megaterium ATCC 14581 could be induced about 28-fold by phenobarbital. We have now examined 19 barbiturates and found that 13 significantly induce the specific monooxygenase activity. Of these, 11 are more active than phenobarbital and three (secobarbital, thiamylal and methohexital) are more than 30 times as active on a molar basis. The dialkyl barbiturates without exception show an excellent correlation between increasing lipophilicity and increasing potency as inducers as do most of the barbiturates containing an aromatic substituent. Nevertheless, it is apparent that certain structural features involving factors other than lipophilicity are also necessary for induction. Our finding that barbiturates can cause the non-substrate induction of a cytochrome P-450-dependent monooxygenase in a prokaryote represents a unique discovery that may provide a relatively simple model for apparently similar induction systems in higher animals.

Incorporation of linolenic-1-C14 acid into eicosapentaenoic and docosahexaenoic acids in fish

Following intraperitoneal injection of methyl linolenate-1-C14 into kelp bass,Paralablax clathratus, the highly polyunsaturated fatty acids of their body fats were concentrated by low temperature crystallization from acetone, and eicosapentaenoic and docosahexaenoic acids were isolated from the concentrate by reversed-phase chromatography and hydrogenated. The resulting arachidic and behenic acids were degraded stepwise to margaric acid, and the distribution of activity was determined. The results indicate that the injected linolenic acid was converted to eicosapentaenoic acid and the latter incorporated into docosahexaenoic acid. A probable conversion pathway is linolenic acid→6,9,12,15-octadecatetraenoic acid→8,11,14,17-eicosatetraenoic acid→5,8,11,14,17-eicosapentaenoic acid→7,10,13,16,-19-docosapentaenoic acid→4,7,10,13,16,19-docosahexaenoic acid.

Characterization of the protein expressed in Escherichia coli by a recombinant plasmid containing the Bacillus megaterium cytochrome P-450BM-3 gene

SummaryIn two previous reports (Narhi LO, Fulco AJ, J. Biol. Chem. 261: 7160–7169, 1986; Ibid., 262: 6683–6690, 1987) we described the characterization of a catalytically self-sufficient 119000-dalton P-450 cytochrome that was induced by barbiturates in Bacillus megaterium. In the presence of NADPH and O2, this polypeptide (cytochrome P-450BM-3) catalyzed the hydroxylation of long-chain fatty acids without the aid of any other protein. The gene encoding this unique monooxygenase was cloned into Escherichia coli and the clone harboring the recombinant plasmid produced a protein that behaved electrophoretically and immunochemically like the B. megaterium enzyme (Wen LP, Fulco AJ, J. Biol. Chem. 262: 6676–6682, 1987). We have now compared authentic P-450BM-3 from B. megaterium and putative P-450BM-3 isolated from transformed E. coli and have found them to be indistinguishable with respect to chromatographic and electrophoretic behavior, reaction with specific antibody, prosthetic group (heme, FAD and FMN) analyses, spectra, enzymology, limited trypsin proteolysis and partial amino acid sequencing. We thus conclude that the P-450 cytochrome expressed by the transformed E. coli is essentially identical to native P-450BM-3 induced by barbiturates in B. megaterium. The evidence furthermore suggests that the primary amino acid sequence of this complex protein is alone sufficient to direct the proper integration of the three prosthetic groups and to specify folding of the polypeptide into the correct tertiary structure.

Hydration of 9,10-epoxypalmitic acid by a soluble enzyme from Bacillusmegaterium

Abstract A soluble epoxide hydrase which catalyzes the hydration of 9,10-epoxypalmitic acid has been partially purified from cell-free preparations from Bacillus megaterium ATCC 14581. The hydrase can be cleanly separated from a soluble cytochrome P-450-dependent monooxygenase complex, previously demonstrated in this bacterium, that can catalyze the epoxidation of palmitoleic acid.

formation of 9,10-epoxypalmitate and 9,10-dihydroxypalmitate from palmitoleic acid by a soluble system from Bacillusmegaterium

Abstract A soluble, cytochrome P-450-containing system from Bacillus megaterium which catalyzes the monohydroxylation of long-chain saturated fatty acids has now been found to convert palmitoleic acid to 9,10-epoxypalmitate and 9,10-dihydroxypalmitate in addition to the expected isomeric mixture of monohydroxypalmitoleic acids.

Carbon monoxide and hydroxymercuribenzoate sensitivity of a fatty acid (ω-2) hydroxylase from Bacillus megaterium

Summary A soluble monooxygenase system from Bacillus megaterium , which hydroxlates fatty acids primarily in the (ω-2) position in the presence of NADPH and 0 2 , is 50% inhibited by carbon monoxide at a CO:0 2 ratio of 0.25 and 85% inhibited by 5 μM p-hydroxymercuribenzoate. The latter inhibition can be reversed by ferredoxin, cysteine or glutathione. These data are interpreted as indicating the involvement of a P-450-type cytochrome and a ferredoxin-type component in the hydroxylation. This system is not inhibited by superoxide dismutase, catalase or by moderate concentrations of various hydroxyl radical scavengers.

Molecular cloning, coding nucleotides and the deduced amino acid sequence of P-450BM-1 from Bacillus megaterium.

The gene encoding barbiturate-inducible cytochrome P-450BM-1 from Bacillus megaterium ATCC 14581 has been cloned and sequenced. An open reading frame in the 1.9 kb of cloned DNA correctly predicted the NH2-terminal sequence of P-450BM-1 previously determined by protein sequencing, and, in toto, predicted a polypeptide of 410 amino acid residues with an Mr of 47,439. The sequence is most, but less than 27%, similar to that of P-450CAM from Pseudomonas putida, so that P-450BM-1 clearly belongs to a new P-450-gene family, distinct especially from that of the P-450 domain of P-450BM-3, a barbiturate-inducible single polypeptide cytochrome P-450:NADPH-P-450 reductase from the same strain of B. megaterium (Ruettinger, R.T., Wen, L.-P. and Fulco, A.J. (1989) J. Biol. Chem. 264, 10987-10995).