ba

Landman and Beier- Neurospora Lactase. I. Properties of Lactase Preparations
———— froma lactose utilizing and a lactose non-utilizing strain.

This paper is an introductory contribution of considerable merit on a subject
of great interest and importance. In general, this reviewer has no doubt as

to ite acospashility. However, it has not been carefully edited by the writers,
ani should be revised in erder to male 14 understandable and conformable to
proper standards of scientific expression.

The reviewer finds two points in the argument inadequately supported. The
evidence an pages 9 and 10 does not seem to have very critical bearing on the
conclusion thet "hydrolytic eleavage representa the major way in which lactose
ie utilised’, for aw might easily imagine that within the mycelium the
lactase system functioned differently than in extracts, or alternatively that
the major pathway of lactose utilisation was mediated by another enzyme whose
adaptive responses peralle]l those of the hydrolytic lactase. Precedents for
both t$pes af action ean be cited! eogse, transphespheatase (Axelrod), and
S-slucosidase in relation to maltase in yeast, respectively. the other
hand, the reviewer regards this issue as overemphasized 4n relation to the
problem of gene-enzyme pentrol, and the writers’ general conclusions are not
greatly affected by this point.

The second issue is more important. Although some interesting details are _
given, thie paper does not present an exhaustive study of the lactase as
enzyme. Its main interest is in the comparison of the lactases of the s

and a “lactoseless* mitent. Prom this point cf view, the behavior of the mutant,
especially ite growth and adaptive enzyme responses to lactose, are not adequately
documented. One may infer that thie is taken up in a companion papet “in prose".
Unless this paper, reference 16, and to seme extent 21, is to adjoin the
present paper in the pages of this journal, the reviewer questions the utility
of splitting the informations At ony rate, he is, to a large extent preventod
from an adequate critical view of the present paper by a lack of information

on the details of the other.

The discussion is rather long, but well—taken and should not be shortened. The
recent papers of Cohn and Monod (Acta Biochim Biphys, 1951) and of Lederborg

and Beadle (both in Genetics in the 20th Century, Maclillan, 1951) are all, however,
extremolyppertinent and should be cited.

The following remarks concern the form rather than the centent of the paper and
are addressed to authors primarily for their am eonsideration: —
1. Capitalization is inemsistent and often incorrect in expressions such
as Ethanol, Minimal Medium, Standard Strain, Lactose. The entire paper should
be carefully edited for orthographic errors. The same for abbreviations and
contractions, especially mg /mge, ml / le, and so forth. Volize numbers
are inconsistently treated in the References. Reference 16 cites Ady. in
Enzymes 19 shown Adv. Ensyn.

—2."B", used repeatedly before "-galactosidase’ should be read (beta) _

3- The datum "rpm", ppe 6, 11 is not useful. "ROF* should be given, or mention
of the type af centrifuge, oo

Lo

fo
4. "lactoseless" ’ ‘pe 2, and throughout. This expression is bound to be
confusing and should be df&scoura if theauthors agree. It is incon-
with the usage in, for example, thionineless", which implies an
organism lacking the ability to synthesize methionine. Sene organi ans
are known which require tryptophane; others cannct metabolize it. Te
use the “-less" terminology for both eases would be very unfortuamte.
Suggested alternatives: lactase-deficiont, alactatic, or lactose-negative.
Specific (mist)conetructionst = —— '

Pe he 8t which/ thet. result and resulted 1
be 4 Ie vitamin formation a mitent charagter?

The second sentence of this paragraph fie avlorard.

Pe 5 Ref. (13) should he moved faxmort beck ene phrase. Emaracn's
deseription of hie strains’ behavior on lactese. should be cited
(Fed. Prec. 1945-671)

a ete carbehydrate

po A P.2 2% by weight ete./ 20 g of carbon source was added per 1.

p. 6 be 6-9. Cation in buffer is net spesified, but presumably K.
WE / PHS or pH Se a |
Le 19 incomprehensible. Do writers meant “ Activities of differcnt
preparations are expressed in terme of constant dry weights of
mycelium per unit volume per wit time" ?
7 le 5S 3.3 for three and’ a third.
Ge 11 implies/ requires
pe 8 Le 1. Concentrations’ levels
(21 Oenfusing! Insert: “activity jn myeskia grom on*
Pe9 Le 1 alternate/ alternative
10 "dealing" dangles.
10 9 Two ideas in one sentence confuse!
12-5 ff. One paragraph only
12 14, and 13,7 calories/zole.
12 7 The expression “ensyme-QiFG reaction’ is vague. It might, but
apparently dees not,refer to the initial reaction of adsorption

ef substrate for which K, is given lates. Since no indication of
extrapolation for Vnax 18 given, it is difficult to determine whekher

the temperature effects concern z x, or Vax » o both, in view af
the non-linearity.
pe 14 Le 1 Same comment. (See Cohn and Monod for offects of cations
on laetose/MPG activity.

14 4 Ee colit Eschorichia or Entamoeba 7

156 Why not document thist The inhibitions themselves, especially
by xylose, would me ae interests .

Legends for figures:
5s This figure is a plot of 1/e against. 1/8 , not a"Kidteslis emctakt’
The abciesa de incorrectly labelled. If the caloulations for pel5
are correct, it should reed 1/ 8 z a, Moet ef the 8 omcentrations
are too low to be useful in the precios eotination of K.. It must
have been rather atetioult to make en accurate detornination of
the first-order rate constants fer an dnitial substrate concentration
ef 265 x 1075 4 (che rightmost points).
ie K, te 4x 1074, ant the assay systen 2 x 10°? ¥, the
etatenent oh pe 7 that the reastion is first order wiier these
conditions is not quite corrects When half the substrate has boen
used up, the rate vould have decreased only about 15% from initial.
Commerrte above on ps 12, 7, fellewed your conclushm a this, but
the enzyme is actually about 40% saturated.
Snaomary?
Reurespora evassa (should be wilerlined). Note! the specific nano
ie never given in the text- why in the spmaryt