Endogenous rhythm, enzymes

Note For some important recent papers dealing with the subjects of Chap. 4, in particular with endogenous rhythms of enzyme activities, properties of PEP carboxylase and intracellular malase transport, the Appendix on pp. 199— 201 should be consulted. 

In a series of extensive and detailed studies, Queiroz has reported much evidence that both CO2 production and fixation are rhythmic. The circadian rhythm of CO2 exchange is thus explained by Queiroz (1974) in terms of endogenous rhythms of enzyme activity (cf. Chap.4.2.3.2,b). Queiroz s data on enzyme capacity indicate that the rhythm of CO2 fixation is an overt indication of actual P-enolpyruvate carboxylase activity which oscillates synchronously with CO2 fixation (Queiroz, 1974). Similarly, the rhythm of CO2 production follows the enzymic capacity of the endogenously controlled malate enzyme (see Fig. 4.6 for the rhythmic phases of PEP carboxylase, malate enzyme, and malic acid). 

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