Reversal by pyruvate of flouride inhibition in Aspergillus terreus

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  • 628 PRELIMINARY NOTES

    metabolism in the lens has thus been demonstrated. These results, if confirmed, would indicate a stimulatory effect of parathyroid hormone upon glucose utilization, as proposed previously z.

    This investigation was supported in part by grant B-3oI6 from the National Institute of Neurological Diseases and Bhndness, U.S. Public Health Service. The author would like to express his appreciation to Dr. G. W. IRwin and the Eli Lilly Company for a generous gift of parathyroid extract which was used in these studies.

    Department of Ophthalmology, H.E . FIRSCHEI~ New York University School of Medicine, New York, N.Y. (U.S.A.)

    x H. E. FIRSCHEIN, W. F. NEUMAN, G. R. MARTIN AND B. J. MULRYAN, Recent Progr. in Hormone Research, 15 (1959) 427 . H. E. FIRSCHEIN, Trans. N.Y. Acad. Sci., in the press.

    a H. E. FIRSCHEIN, Conf. on Connective Tissue, Wayne State Univ., Detroit, in the press. 4 D. B. KIRBY, Trans. Am. Acad. ophthalmol., (193 o) 154. 5 C. S. O'BRIEN, Arch. ophthalmol., 7 (1932) 71. 6 L. JACQUES, Am. J. med. Sci., 175 (1928) 185. "l L. R. DRAGSTEDT, A. C. SUDAN, AND K. PHILLII~S, Am. J. Physiol., 69 (1924) 477. 8 E. I. EVANS, AND R. KERN, Am. J. ophthalmol., 14 (1931) lO29. 9 S. E. BROLIN, Acta Ophthalmol., 31 (1953) 485 .

    10 j . NORDMANN, P. MANDEL, AND M. ACHARD, Brit. J. Ophthalmol., 38 (1954) 673. 11 W. W. UMBRI~IT, 1{. H. BURRIS, AND J. F. STAUFFER, in Manometric Techniques, 3rd ed., Burgess

    Pub. Co., Minneapolis, 1957, p. 149. 12 G. GUIDOTTI, J. P. COLOMBO, AND P. P. FOA, Anal. Chem., 33 (1961) 15I. 13 S. B. BARKER, AND W. H. SUMMERSON, J. Biol. Chem., 138 (I94 I) 535.

    Received February 9th, 1962 Biochim. Biophys. Acta, 58 (1962) 626--628

    Reversal by pyruvate of fluoride inhibition in Aspergillus terreus

    The Embden-Meyerhof reactions appear to represent the major pathway for the dissimilation of glucose in Aspergillus terreus 1. In strains producing itaconic acid, fluoride has been shown to inhibit the utilisation of glucose as well as the formation of itaconic acid 1, ~. In this communication we describe some unusual phenomena as- sociated with fluoride inhibition in one such strain, Asp. terreus NRRL 265.

    The mold was grown in surface culture at 320 on 5o ml of a medium (pH 3) containing cane sugar (approx. 15 %), NH4NO3 (0.2 %), MgSO 4. 7H~O (o.I %), and KHzPO4 (o.o2 %), in 25o-ml conical flasks. After 6-8 days, the sugar-depleted medium was replaced by 50 ml of fresh medium to which NaF and sodium pyruvate had beet~ added ir~ the required concentration. After 8 days, the mats from 2 identically treated flasks were analysed for their content of itaconic acid and of reducing sugar by ti~e methods of FR~EDKIN s and NATELSON et a~. 4, respectively.

    At a coneemtrati~a of 0.4 mM, fluoride had very little inhibitory effect on the utilisation of sugar by the mold, although the formation of itaconic acid was inhibited by over 9 %. As the concentration of fluoride was increased, sugar utihsation was ~ess ive ly inhibited; 4 mM fluoride inhibited almost completely the utilisation of sugar as well as the formation of itaconic acid, as reported for Asp. terreus NRRL 196o ~y BENTLEY AND THIESSEN 1.

    Biochim. Bio~hys. Acta, 58 (1962) 628-630

  • PRELIMINARY NOTES 629

    Pyruvate reversed the inhibit ion of sugar util isation as well as of itaconic acid formation by fluoride. The results of two typical experiments, in which the effect of the addition of various concentrations of pyruvate to cultures of the mold inhibited by fluoride at several concentrations was studied, are given in Table I. The amount of pyruvate required to reverse the inhibit ion by fluoride of sugar uti l isation and of itaconic acid formation was found to depend on the concentration of fluoride in the culture. The reversal of the inhibit ion of sugar uti l isation did not, however, go hand

    TABLE I

    EFFECT OF PYRUVATE ON FLUORIDE- INHIB ITED CULTURES OF AN ITACONIC ACID-PRODUCING STRAIN OF .ASp. te~'~'e~A$

    For composition of the basal medium, see text. The initial sugar concentration in the 2 experiments was 14. 9 % and 15. 7 %, respectively. All the values in the last 2 columns for each experiment,

    are for 2 flasks, each containing 5 ml of the medium, pooled together.

    Expt. x Expt. 2

    Additions to basal medium

    Fluoride Pyruvate (raM) (raM)

    Sugar Itaconic acid Additions to basal medium Sugar Itaco~ic acid consumed formed Fluoride Pyruvat~ consumed formed

    (g) (g) (raM) (raM) (g) (g)

    o o 12.1 4.5

    2 O 0 .2 0 .2

    2 45 9.7 i. i 2 91 12.2 3.1 2 136 13-6 4.4 2 182 14.8 5.4 2 273 14. 9 6.2

    o o 13. 5 5-5

    I O 2. 9 0 ,2

    I 91 15.7 5,o I 182 15. 7 5.8

    1.33 o 2.1 0.2 1.33 91 14.5 4.2 1.33 182 15. 7 5.5

    2 o 1.4 o.2 2 91 14.5 3.7 2 182 15. 5 5.4

    4 o 1.6 0.2 4 91 12.o I. 5 4 182 13. 3 2.9

    IO O 0. 9 0 .2 IO 91 8.o o.6 IO 182 12. 3 I.I

    in hand with the reversal of the inhibit ion of itaconic acid formation; more pyruvate was required for complete reversal in the latter case than in the former, at all the fluoride concentrations tried (I-IO raM). For example, in the presence of 2 mM fluoride, in a typical experiment (Table I, Expt. I), 45 mM pyruvate reversed the inhibit ion of sugar util isation and of itaconic acid formation by 78 and 25 %, re- spectively; with 91 mM pyruvate, the reversals were Ioo and 69 %, respectively. 136 mM pyruvate completely reversed the inhibit ion of itaconic acid formation, and effected the util isation of 12 % more sugar than in the control lacking fluoride and pyruvate. In the presence of o.273 M pyruvate, the amount of sugar utilised and the total yield of itaconic acid were, respectively, 23 and 38 % in excess of thos, obtained in the control.

    Biochim. Biophys. Acta, 58 (1962) 628-63

  • 6~0 PRELIMINARY NOTES

    The above observations on the inhibition of sugar utilisation and of itaconic acid formation by fluoride, and on the reversal of these inhibitions by pyruvate, suggest that fluoride has two sites of action in itaconic acid-producing strains of Asp. terreus, One of these sites must be a step in the normal glycolytic scheme, presumably that catalysed by enolase [D-2-phosphoglycerate hydro-lyase (phosphopyruvate hydra- tase), EC 4.2.1.11] which has been reported to be the enzyme most susceptible to fluoride out of all the enzymes so far tested. The other site of action would appear to be some step in the conversion of pyruvate to itaconic acid. Since this step is inhibited by concentrations of fluoride which do not appreciably inhibit glycolysis, and since the block in the biosynthesis of itaconic acid remains even after the inhi- bition of sugar utilisation is completely reversed, it would appear that enohse is not the enzyme which is most susceptible to fluoride in itaconic acid-producing strains of Asp. terreus. The nature of the "second" site of fluoride action in this mold is not yet clear, and is under investigation. Since alI the enzymes involved in the con- version of pyruvate to c/s-aconitate via acetyl-coenzyme A and citrate are known to be less susceptible to fluoride than is enolase, and since cis-~comtate decarboxylase (EC 4.1.1.6) 1 is unlikely to be mote suscept~le to fluoride tharr is enolase, itaconic acid would appear to be formed in Asp. tz~eus from pyruvate ~. without the inter- mediate formation of ace~yl-coenzyme A and/or citrate. As the work of BENTLEY AND THIESSEN 1 leaves no doubt that c/s-ac~mitate is the immediate precursor of itaconic acid, our observati~ts impl3~that in A~. temeus, cis-aconitate can b~ formed. from pyruvate by a pathwa~ other t~mn the umial one involving acetyl-coermyme & and citrate.

    The complete reversal by ]~rruvatm of fluolfiile inlu'bition does not appeaar to have, been reported earlier, and ii~ mechamism is not yet understoocL Pyruvate ma~ mediate in the conversion of fffw~ide t~an inactive derivative. For ~tample, pyruvai~e could be first metabolised thremgh the~mormal oxidative patltway (~particul~rly if tlm itaconic acid pathway is blocimd), ano~ the ATI~ formed during tl~e oxidation couP! react with fluoride in the presence of t~ pyruvate kinase (EE 2.7=x.4o) of the moki s, to give FH~POa. The fluoroplmsphate thus formed may hOlt be am inhibitmr of glyco- lysis. This possibility is being currently investigated. Although pyruvate~ is known to inhibit the fluorokinase activity o~ pyruva~e kinase, tiffs inMbition occurs oaly at high concentrations of pyruvate {for a 4~z% inhibition, o~o34 M pyruvate is requited in a purified systemS).

    We are very grateful to Dr. S. HUSAIN 7~W~_R for his encouragemeat.

    R~mmd R~utrd~ Laboratory, Hydembad (I~Zi4) Mo~ LAL P. M. BHXSGAVX

    R. ~mm~t-~-~e. Tmmmm, J . Biot. C/u~., 226 (x957) 673, 689, 7o3. t p_ ms. B~kw~UtVA. K. RAMAC~ANDRXN. S. RAo, M. Lax. xm~ S. H. ZAHEmt, in O. Hc~x~m~t-

    Osam~m~ Pm. IV. I~ . Coa~. Biochem., Vi~tta, I958 , Pergamon Press, Inc., London,

    s ]K .~Ia~LEatg . Chem., x7 (x945) 637. * S ~ ~ J. ]3. PINcu$ A~ J. K. LUGOVOY0 J . B/o/. Chem., I75 (x948) 745. A. Tnrrff i-m~ S~ ~ . Am~h. Biochem. Bio~ys. , 78 (x958) 477.

    Rece i~ '~ ~. x#2

    Biochim. Biophys. Acta, 58 (x962) 628-630

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