COMMUNICATIONS T O T H E EDITOR THE ENZYMATIC CARBOXYLATION OF ACETYL
with 500 pmoles of hydroxylamine hydrochloride for ten minutes a t 23'. Hydroxamic acids were SiT: extracted and chromatographed on Whatman X . 3 Recent experiments indicate that the enzymatic filter paper in water-saturated butan01.~ Monosynthesis of fatty acids probably occurs via an al- malonyl hydroxamic acid exhibited an Rfof 0.36 in dol condensation of the Knoevenagel type between this system. The chromatogram was examined aliphatic aldehydes and malonyl coenzyme Ale2 with a strip counter, and the major portion of the (malonyl CorZ) . The carboxylation of propionyl radioactivity was localized in the region between COX and /3-methyl-crotonyl-COX in the presence of Rf 0.33 and 0.41. For additional identification, CO? and adenosine triphosphate (ATP) has been the supernatant solution from an acid-deproteiI1demonstrated. Experiments were undertaken ized incubation mixture was extracted for 1s hours to determine if such a reaction could be observed with ethyl ether. The radioactivity remained in between acetyl COX and HCOa- to form malonyl the aqueous phase which was therefore adjusted t o COX. pH 9.0 with 2 N potassium hydroxide and heated Extracts of pig heart tissue were prepared: and for 90 minutes a t 50'. The solution was re-acididialyzed overnight against 100 volumes of 0.02 AI fied and extracted with ether. The radioactivity Tris buffer, pII 7.4. Extracts of pigeon liver tissue was now present in the ether phase. The ether exwere prepared6 and the fraction precipitating be- tract was dried over sodium sulfate arid the solvent tween 0 and 30y0 saturation with ammonium sul- was removed. The residue was taken up in 255;. fate was taken up in 0.04 M K H C 0 3 and dialyzed methanol and chromatographed on paper accord~ acid exhibited against the same solution for four hours. Enzymes ing to Flavin and O ~ h o a . Malonic present in these extracts catalyzed the fixation of an Rfof 0.53 in this system. Searly all of the raHC"03- (Table I). The reaction catalyzed by ex- dioactivity was confined to this region of the chrotracts of pig heart tissue was found t o be dependent matogram. upon supplemental ATP, acetyl CoA, and Mg++ (7) 0. Hayaishi, J . Bioi. Chem., 215, 125 (1955) ions. The fixation of Cl4O2 catalyzed by pigeon A-ATIONAL INSTITUTE OF KEUROLOGICAL liver preparations was dependent upon suppleJOSEPH V. FORMICA DISEASESAND BLINDNESS mental A T P and RlgCle and was markedly en- BETHESDA, ROSCOE0. BRADT MARYLAND hanced by the addition of acetyl COX. RECEIVEDDECEMBER 3. 1938 COENZYME A
TABLE I OF CL402 B Y ACETYL COENZYME A FIXATION The reaction mixtures contained 80 pmoles of imidazole hydrochloride buffer, p H 7.0, 3 @molesof MgCl2, 3 pmoles of ATP, 1 pmole of K H C L 4 0 $(9 X lo5 c.p.m.), 1 pmole of acetyl CoA, extract of pig heart tissue ( 3 mg. of protein, Experiment 1) or pigeon liver ( 5 mg. of protein, ExperLment 2 ) in 1.0 ml. Bfter incubating for 60 minutes a t 30 , 0.2 rnl. of 2 N perchloric acid was added and the amount of fixed radioactivity was determined as described by M. Flavin, 11. Castro-Mendoza and S. Ochoa, J . B i d . Chem., 229, 981 (1957). Experiment no.
1. Pig heart extract
2.
Pigeon liver extract
Reactant omitted
Sone
.ITP Acetyl Co.1 hlgC12 Sone ATP .qcetyl CoA JIgClp
C''O0, fixed, c.p.m.
2050 20 60 50 763 48 380 40
T o identify the product of the reaction, an aliquot from an acid-deproteinized sample of the pig heart preparation was neutralized and incubated a $ . A c a d . Sci., 44, 993 (1958). (1) R. 0 . Brady, PTUC. U. ( 2 ) D. M. Gibson, E. B. hener and S. J. Wakil, Biochim. el Biophys. A d a , 30, 376 (1958). (3) h l . Flavin and S. Ochoa, J . Bioi. Chem.. 229, 965 (1957). (4) J. Knappe a n d F. Lynen, "Abstr. IV International Congress of Biochemistry," Vienna, Austria, 1958, p. 49. ( 5 ) B. K . Bachhawat and If. J . Coon, J . Riot. Chem., 231, 625 (1958). (6) S . J. Wakil, 5 , W. Porter and D . X f . Gibson, Biochim. ~f R i o p h y s . A d a , 24, 453 (195i).
A METAL CARBONYL COMPOUND OF TITANIUM
Sir: Metal carbonyl compounds of the Group IV-R transition metals have not been reported previously. The titanium carbonyl derivative, bis(cyclopentadienyl) -titanium dicarbonyl (I) has now been prepared by the reaction of bis-(cyclopentadieny1)-titanium dichloride (11) in benzene with two equivalents of cyclopentadienyl sodium, and then treatment of the intermediate product with carbon monoxide a t 135 atm. and 100' for eight hours. -1nalysis of the crude reaction product by measurement of the carbon monoxide evolved on treatment with iodine2 indicates t h a t a 50y0overall yield of the carbonyl is present in the reaction product. The extremely air sensitive carbonyl can be isolated in pure form in an over-all yield of lSyOby removal of the benzene from the reaction product and then recrystallization from air-free hexane (all operations under nitrogen). Dark reddish brown crystals of I are obtained which decompose above 90' under nitrogen. Anal. Calcd. for CI2Hl0Ti02: C , 61.56; H, 4.31; Ti, 20.40. Found: C, 61.5G; H, 4.55; Ti, 20.38. (1) T h e possibility of preparing metal carbonyl compounds of the Group IV-B metals has been anticipated b y J. E. Brown and H. Shapiro in U. S. P a t e n t 2,818,416 ( t o E t h y l Corp.) December 31, 1957. (2) H . W.Sternherg, I. n'ender and RZ. Orchin, A n a l . Chem., 24, 174 (1Y33.
