TY - JOUR
T1 - Identification of the enzymatic lesions responsible for the accumulation of acetylated sphingosine bases in the yeast Hansenula ciferri
AU - Barenholz, Yechezkel
AU - Gadot, Nathan
AU - Valk, Eliyahu
AU - Gatt, Shimon
N1 - Funding Information:
in the high as comparedw ith the low producer, thus confirming previous results2. The above results demonstratet he existenceo f two enzymesw hose activitiesa re greateri n the high producer. The condensinge nzyme (i.e. that catalyzing the interaction of serinea nd palmitoyl-CoA to form 3-ketodihydrosphingosine,s ee Fig. 1) and the acetylatinge nzyme (catalyzing the transfer of acetyl groups to the amino and hydroxyl groupso f the sphingosineb ases).T he genetica spectsle ading to a dual metabolic lesion in the respectives trains of Hansen& ciferri have yet to be analyzed. The relative rateso f the four enzymess uggestt hat the condensation of palmitoyl-CoA and serinem ight be the rate-limiting step in the biosynthesiso f sphingosineb asesi n this yeast.A n increaseo f either the quantity of this enzymatic protein or of its specific activity would markedly affect the biosynthetic rates,a nd might account for the nearly lOOfold increased,i n vivo production, of the sphingosineb asesi n the high producers. This work measuredo nly the synthesiso f dihydrosphingosine,w hile the high producersa ccumulatem ostly acetylatedp hytosphingosine.W e could not study the rateso f synthesiso f the latter base,s ince no in vitro systemi s availablew hich convertsd ihydro-sphingosinet o phytosphingosine.I t is worth mentioning, in this respect,t hat when a high-producing yeast was grown in the presenceo f 3H -labelled dihydrosphingosine,3 H -labelled phytosphingosinew as formed (ref. 11 and unpublished results). This work was supportedi n part by grantsf rom the N.I.H. (NS-02967) and The National Tay-Sachsa nd Allied DiseasesA ssociation of the U.S. N. G. was on leavef rom the Central NegevH ospital, Beer-Sheva.
PY - 1973/5/24
Y1 - 1973/5/24
N2 - The enzymatic lesions responsible for the accumulation of acetylated sphingosine bases in the "high producer" strains of the genus Hansenula were studied. Two strains, one a "low" and the other a "high" producer, were selected to compare four enzymatic steps leading to the synthesis of acetylated dihydrosphingosine by yeast microsomes. Both strains were very similar in their generation time and DNA content, but the high producer accumulated 150 times more sphingosine bases than the low producer. Among the four microsomal enzymes, the specific activity of the palmityl thiokinase and 3-ketodihydrosphingosine reductase were almost identical in the two strains. In contrast, the specific activity of the 3-ketodihydrosphingosine synthetase, which catalyzed the rate-limiting step in dihydrosphingosine biosynthesis, was 5-10-fold greater in the high producer strain than in the low producer. The long-chain base-acetyl-CoA acetyltransferase was at least 30 times more active in the high as compared with the low producer. It therefore seems that the latter two enzymes may be the cause for the in vivo accumulation of acetylated sphingosine bases in the high producers.
AB - The enzymatic lesions responsible for the accumulation of acetylated sphingosine bases in the "high producer" strains of the genus Hansenula were studied. Two strains, one a "low" and the other a "high" producer, were selected to compare four enzymatic steps leading to the synthesis of acetylated dihydrosphingosine by yeast microsomes. Both strains were very similar in their generation time and DNA content, but the high producer accumulated 150 times more sphingosine bases than the low producer. Among the four microsomal enzymes, the specific activity of the palmityl thiokinase and 3-ketodihydrosphingosine reductase were almost identical in the two strains. In contrast, the specific activity of the 3-ketodihydrosphingosine synthetase, which catalyzed the rate-limiting step in dihydrosphingosine biosynthesis, was 5-10-fold greater in the high producer strain than in the low producer. The long-chain base-acetyl-CoA acetyltransferase was at least 30 times more active in the high as compared with the low producer. It therefore seems that the latter two enzymes may be the cause for the in vivo accumulation of acetylated sphingosine bases in the high producers.
UR - http://www.scopus.com/inward/record.url?scp=0015934666&partnerID=8YFLogxK
U2 - 10.1016/0005-2760(73)90239-7
DO - 10.1016/0005-2760(73)90239-7
M3 - Article
C2 - 4713160
AN - SCOPUS:0015934666
SN - 0005-2760
VL - 306
SP - 341
EP - 345
JO - Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
JF - Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
IS - 2
ER -