5. ONIUM COMPOUNDS
211
0
H 2 N
ΗΝγ
"Ν'
CH 3
I
CHO
H 2 N
HN
j
CH 3
I
CH 2
I
CHOH
CH
/
o
CH
CH 2 OP0 3
2 -
CH 2
I
CHOH
I
CH
O
CH 2 OP0 3
2
~
(I)
(Π)
o
CH3
I
H 2 N
N N' \N*
+
OH
I
CH
I
CH 2
I
CHOH
AHO +ΗΘ
CH 2 OP0 3
2 -
(III)
FIG. 10. Mechanism of hydrolysis of 7-methyldeoxyguanylic acid at pH 7.0.
conditions originally employed for the preparation of methylthioadenosine from yeast, S-adenosylmethionine would break down to methylthioadenosine and homoserine, it was suggested by Baddiley et al.
(129) that the yeast nucleoside was in reality adenosylmethionine from
which the simpler sulfur-containing nucleoside would arise during the
NH
\-H
C H—CH (OH)—CH (OH)—CH—CH 2 —S
-OFIG. 11. Methylthioadenosine.
CH 3
extraction procedure. Recent work of Schlenk and de Palma (141),
and of Mudd (142) in the author's laboratory has confirmed this hypothesis in that it has been shown that, if care is taken to exclude the
possibility of hydrolysis of the sulfonium compound during extraction,
yeast grown in the presence of methionine contains large amounts of
S-adenosylmethionine and only little methylthioadenosine (Table IV).