YALE UNIVERSITY
OSBORN BOTANICAL LABORATORY
NEW HAVEN, CONNECTICUT

Novcanber 6, 1946.

DeE'r i501:

;lim's the Genius? (That is Leeyvi's description; I heard it

pit? my own ears this su er ;bct ds ~lo~e.)

   Bonnei just let me see zL cosy of your rnzmAscript, t.m reztciing
it nas&jst like being at Cold aping htrbour, iiea?ink one line of
Pvidence after snotller until one Is almost compelied to s:3y:bt,o,,
IT11 believe 3nything yolj say, It i2 yuitc tiirilling, f-nytking new?

There is only one polhlht which is not mite clear to me, snc; tliat

is the deteil Qf the postul; ted mechznism of substrFte-enzyme
interEIctions, particularly betv:?.esn different syst-ms. Vmt, jcan$~xf
do yor, propose is tile mekenism by -irizich tLe formztion of' t second
enzym depletes tLe first ; why skoula trip 2rk;sence of ExogenoLs
3? af,"ect this process if the substrates are sim1,iy conipting on
 instable enzyme aolecules? Khy &re tLe enzyincz less uri&t~b&k i11 tk
pr sence of hzide? All of trese que.tions are bLsed on titis con-
ception of thp role of subst,i-cte: tht the precursor sufiers rancAom
reversible chxges, o ccasionally poducing enzymetick liy syec6;ic

mo.ecules, End tkt tiieze& zre stsbilized by the prebence of tiie
substrate. :!ocever, it is dif'ficE:lt :or ne to se~ thtl role of a

,on6 ?nother Siwhe3ical mutant6 ~~rhich is Lrlus kre crosseci, in the

yrcsence mi sbsence of lactose. iny sug:,c. tiom?

Sincerely,