The Journal of General and Applied Microbiology
Online ISSN : 1349-8037
Print ISSN : 0022-1260
ISSN-L : 0022-1260
HYDROGEN SULFIDE EVOLUTION DUE TO PANTOTHENIC ACID DEFICIENCY IN THE YEAST REQUIRING THIS VITAMIN, WITH SPECIAL REFERENCE TO THE EFFECT OF ADENOSINE TRIPHOSPHATE ON YEAST CYSTEINE DESULFHYDRASE
TAKASHI TOKUYAMAHIROSHI KURAISHIKO AIDATEIJIRO UEMURA
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1973 Volume 19 Issue 6 Pages 439-466

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Abstract

Baker's yeast showed periodical changes in cysteine (CyH) desulfhydration activity with cell growth, and the crude extract from young pantothenate-deficient (PaA-) cells had 1.6 times higher activity than that of pantothenate-sufficient (PaA+) cells of the same growth phase. PaA- cells were also stronger in sulfite reductase activity as examined in 0.6M phosphate buffer. PaA- cells were thus endowed with H2S producibility, although the yeast had more intensive CyH synthetase activity than CyH desulfhydrase one, irrespectively amount of pantothenate supplied. Of pooled amino acids, a larger amount of serine was found in PaA+ cells while CyH only in PaA-cells. A DEAE-cellulose column chromatography of the crude extract enabled separation of unstable CyH desulfhydrase from stable CyH synthetase, and each enzyme, which resembled each other in property, was purified to almost homogeneous level. In Km for CyH desulfhydration activity, CyH desulfhydrase had exceedingly lower value (3.4×10-4M) than CyH synthetase (reversed) (2.0×10-2M), and thus the former enzyme seemed likely to take a predominant part in cell CyH desulfhydration.
Adenosine triphosphate (ATP) as well as S-adenosylmethionine could inhibit CyH desulfhydrase at acid pH while ATP stimulates it at alkaline pH, although ATP was inert to CyH synthetase. A sigmoid curve was depicted in the activity-substrate concentration relation at pH 6.9, and 14C-ATP-enzyme complex was obtained from a mixture of CyH desulfhydrase protein and 14C-ATP when incubated at 30° for 30min. Thus ATP-effect seems likely to occur on the basis of allosteric inhibition, presumably playing a modulating role in prevention of CyH once synthesized from its degradation in yeast sulfur metabolism. A possible mechanism for H2S evolution due to PaA deficiency in PaA-requiring yeast was presented.

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