January 27, 1948.

Dear Jacques,

Thanxy you very much for your manuscript. I have read it carefuliy, and with
great interest. You have not indicated whether you wish it to be returned; I will
hasten to do so at your word.

I have been doing some experiments lately on adaptution for galactosidase
which may interest you. Kel2 will develop this enzyme to varying extents on dif-
ferent substrates. If the activity per cell, as measured with nitrupneny2 zelace
toside, is counted as 100 fcr lactose, the relative activities of cells harvest
from broth with the indicated substance as eecondary carbon source ave os follows:

nebutyl be galactoside 115 This is for Kel2, Lacy= and Lac3~
Luttose 100 atocks do net respond to lactose
LactobLonate 73 but will to butyl galactoside aad to
galactose 23 galactose. Lac... doses not form the enzyme
galactonats under any condition tasted, and the eame
mac ate ca 2 is probably true for Lac ,~ and Lac i=.
dulcitol

l-~arabinose less than 1, probably You can probably see, therefore,

d-glucose due to adaptation during why I have eoncluded that most of the
the sseasurenent (20 mins.) venetic effects are inflirect, and on
the commeterice of the udaptation mechanism.

Gells of ©. coli ~L (1) will split aitrophenyl galactoshie if, «xd they are
grown on lactose, and to a far lesser extent if grown on galactose (5% of the lactose
cells activity.) Glucomegrown cells, of course, have no msagurabie activity. I am
wnclosing a few ng. of nitrophenyl galactoside, for your use if you would pike
to test the actiwity of your "purified" lactase.

For the above table, I should note that lactobionate, which is « very effective
evocator of galactosidase, is not utilizable for grovyth or feruentatica by Kel2.
Likewlse, galactose has the same adaptive potence fcr calactosiduse forration
on mutants which are incapable of using galactose as for Kel2. Thus utilization and
adaptation have been separated in both ways. ( Lactose, for Lacj- is not does not
evoke the enzyne but is utilized by it; lactdbionate is not utilized but does evoke.)

The pH optimm for galactosidase extracts 1s 7.3. For intact cells is is closer
to 7.0 The Na stinulations and Rb inhibitions which have been noted with the extracts
are not demonstrable with the intact eells, indicating that the enzyme nay be pro-
tected. The anp-arent Kn is about jlO™ s almost 4x as high as for the extract, This
difference may be due to the fuct that diffusion is the rate linitinz sten, and this
is being studied.

Good luck on your trip to London, and let we know if unything interesting cones up.
Sincerely,