458
VERNON H. CHELDELIN, CHIH H. WANG, AND TSOO E. KING
change reaction or other similar processes (130) does not occur to any
significant extent.
Most of the foregoing assumptions can be readily verified; this has
been done, in at least one biological system (139) by separate experiments. It should be stressed that in studying the catabolism of a
biological system under normal physiological conditions, such as intent
plants, intact animals, or proliferating microorganisms, it is justifiable
to believe that the catabolic "traffic" associated with a normal substrate
is largely unidirectional toward sequential breakdown leading to the
eventual formation of C0 2 . Consequently, the randomization of labeling
pattern in the substrate through the operation of reversed catabolic reactions is greatly minimized.
(7) The catabolic behavior of substrate gluconate is the same as that
of gluconate derived from glucose via the HMP pathway.
On the basis of the foregoing assumptions, use can be made of the
yields of C
14 0 2 at 1 RTU from C
14 specifically labeled glucose to estimate the pathway participations in the over-all catabolism.
Let G u G 2? G 3 , G 4> G 3j4 and G 6 = percent radiochemical yield of
substrate activity in the respiratory C0 2 , from systems metabolizing
equal amounts of glucose labeled with C
14 at C-l, C-2, C-3, C-4, C-3
(or 4), or C-6, respectively, taken at 1 RTU, at which time the initial
breakdown of administered substrate has been completed. These are expressed as fractions of unity.
A l9 A 2 , A 3 , A 4 , A 3)4 , A 6 = percent C
14 0 2 yields from systems metabolizing equal amounts of gluconate labeled with C
14 at C-l, C-2, C-3, C-4,
C-3,4, or C-6 respectively, taken at 1 RTU, expressed as fractions of
unity.
G T = total radioactivity of each labeled substrate administered (always taken as 100%, or unity).
G' T = fraction of the labeled substrate administered engaged in anabolic processes.
G p = fraction of the administered glucose engaged in catabolic
functions routed via phosphogluconate cleavage.
G e (Embden-Meyerhof) = fraction of the administered glucose engaged in catabolic functions routed via glycolysis.
G e d = fraction of the administered glucose engaged in catabolic functions routed via the Entner-DoudoroflE pathway.
The equations for pathway estimations are given as follows:
(1) With biological systems that catabolize substrate glucose extensively, such as microorganisms, and under the additional assumption
that the pentose phosphate formed in the HMP pathway does not participate in C0 2 production.
VERNON H. CHELDELIN, CHIH H. WANG, AND TSOO E. KING
change reaction or other similar processes (130) does not occur to any
significant extent.
Most of the foregoing assumptions can be readily verified; this has
been done, in at least one biological system (139) by separate experiments. It should be stressed that in studying the catabolism of a
biological system under normal physiological conditions, such as intent
plants, intact animals, or proliferating microorganisms, it is justifiable
to believe that the catabolic "traffic" associated with a normal substrate
is largely unidirectional toward sequential breakdown leading to the
eventual formation of C0 2 . Consequently, the randomization of labeling
pattern in the substrate through the operation of reversed catabolic reactions is greatly minimized.
(7) The catabolic behavior of substrate gluconate is the same as that
of gluconate derived from glucose via the HMP pathway.
On the basis of the foregoing assumptions, use can be made of the
yields of C
14 0 2 at 1 RTU from C
14 specifically labeled glucose to estimate the pathway participations in the over-all catabolism.
Let G u G 2? G 3 , G 4> G 3j4 and G 6 = percent radiochemical yield of
substrate activity in the respiratory C0 2 , from systems metabolizing
equal amounts of glucose labeled with C
14 at C-l, C-2, C-3, C-4, C-3
(or 4), or C-6, respectively, taken at 1 RTU, at which time the initial
breakdown of administered substrate has been completed. These are expressed as fractions of unity.
A l9 A 2 , A 3 , A 4 , A 3)4 , A 6 = percent C
14 0 2 yields from systems metabolizing equal amounts of gluconate labeled with C
14 at C-l, C-2, C-3, C-4,
C-3,4, or C-6 respectively, taken at 1 RTU, expressed as fractions of
unity.
G T = total radioactivity of each labeled substrate administered (always taken as 100%, or unity).
G' T = fraction of the labeled substrate administered engaged in anabolic processes.
G p = fraction of the administered glucose engaged in catabolic
functions routed via phosphogluconate cleavage.
G e (Embden-Meyerhof) = fraction of the administered glucose engaged in catabolic functions routed via glycolysis.
G e d = fraction of the administered glucose engaged in catabolic functions routed via the Entner-DoudoroflE pathway.
The equations for pathway estimations are given as follows:
(1) With biological systems that catabolize substrate glucose extensively, such as microorganisms, and under the additional assumption
that the pentose phosphate formed in the HMP pathway does not participate in C0 2 production.