5. ONIUM COMPOUNDS
193
Scheme 3 can be modified to account for the biosynthesis of miokinine (29) as shown in Fig. 4. Steps 1 and 2 are completely analogous to
steps 1 and 2 in Fig. 3. Step 3 has not been encountered before but, as
will be evident from the earlier discussion, it may be considered as the
(CH 3 ) 3 N
CH 2
CH 2
cf
|
Ns
CH ;
(CH 3 ) 3 N
CH;
CHOH
+
1
CH 3
'
I Jd
CH 2
x CoA
Of
x CoA
2 l -Η2Ο
©
©
(CH 3 ) 3 N
(CH 3 ) S N
I
I
CH 2
CH 2
I
s
I
CH2
>
CH2
I
Θ +
I
CH
(CH 3 ) 3 NH
CH 2
II
®l
CH
(CH 3 ) 3 NCH
^CoA
x CoA
-* Ι+Η2Ο
Φ
(CH 3 ) 3 N
I
CH 2
I
CH 2
I
CH 2 + CoA
Φ|
(CH 3 ) 3 NCH
cooFIG. 4. The biosynthesis of miokinine.
reverse of an elimination reaction from an onium pole, and is quite
possible both on chemical and biochemical grounds. Moreover it has
some analogy to the biosynthesis of /?-alanine from NH 3 and propionylCoA, a reaction recently studied by Stadtman (30). The biological
utilization of trimethylamine would be interesting since trimethylamine
is formed from choline both by aerobic and anaerobic bacteria and by a