An action spectrum for carotenogenesis in V. agaricinum has maxima at 395, 433, 660 and 737 nm. In a previous study it had been shown that a light‐minus‐dark difference spectrum of a crude extract from V. agaricinum had maxima at 390 and 420 nm, and furthermore a red, far‐red interaction suggesting phytochrome involvement has been proposed. All these data suggest that there may be at least two photoreceptor systems operating in the photoinduction process here; one for the near‐ultraviolet (UV‐A)‐mediated carotenogenesis, presumably a novel pigment, and the other for the red, far‐red region, most likely phytochrome.

Aspartate aminotransferase in Leptasphaeria michotii has previously been shown to have an activity rhythm in constant conditions. The enzyme is present as two isoforms whose levels were quantified along the activity rhythm by ELISA, using specific polyclonal antibodies raised against polypeptides purified to a state of apparent homogeneity. The time-course of the level of the cytosolic isoform remained unchanged along the experiment. On the contrary, the cyclic variations in amount and transaminase activity (using cysteine sulfinate as substrate) of the mitochondrial isoform gave rise to the aspartate aminotransferase activity rhythm of the fungus. The mRNA levels of the two isoforms, as determined by in vitro heterologous translation, remained monotonous along the daily cycle. These results and the sensitivity of the rhythm towards protein synthesis inhibitors are consistent with the hypothesis that the aspartate aminotransferase activity rhythm in this species is caused by some mechanism controlling the efficiency of translation of mitochondrial isoform mRNA.

Alanine aminotransferase (EC 2.6.1.2) was obtained from the fungus Leptosphaeria michotii (West) Sacc, and enriched 714‐fold by a 5‐step purification procedure as a dimer of Mr 110000, associated with a polypeptide of Mr 25000. Its isoelectric point was 5.25. The enzyme was active from pH 3.5 to 9.5 with a maximum at pH 7.5. Its specific activity was 6000 nkat (mg protein)−1; the Km was 6.85 mM for L‐alanine and 0.2 mM for 2‐oxoglutarate. The enzyme did not show any detectable activity in the presence of L‐aspartate, cysteine sulfinate, α‐aminobutyrate or cyclic amino acids as substrates. It did not express alanine:glyoxylate aminotransferase activity. Alanine aminotransferase in L. michotii has previously been shown to have an activity rhythm in constant temperature and darkness. The enzyme level was quantified along the activity rhythm by enzyme‐linked immunosorbent assay (ELISA), using a monospecific polyclonal antibody against the purified enzyme. The cyclic variations of alanine aminotransferase activity were correlated with cyclic variations in the enzyme level.

S, 1989, Asparagine and regulation of photoinduced rhythm in Penicillium claviforme. Plant, A photosensitive reaction involved in the expression and regulation of the endogenous sporulation rhythm in Penicillium claviforme Bainier CBS 126-23 has been described earlier by our team. The present work shows that asparagine plays a central role in this periodic system. The 24-26 h periodicity, which becomes desynchronized over a few days, was affected by supplying asparagine (1 to 25 mM), a) The rhythm remained synchronized for at least 3 weeks, for all the asparagine concentrations used, b) The period increased successively from one cycle to the next (from 35 ± 3 h to 73 ± 8 h over 6 cycles) for 1 mM asparagine. This period lengthening became less and less accentuated as the asparagine concentration was increased. At > 10 mM, the period was stable; it was 33 + 5 h for 10 mM and 22 ± 1,5 h for 25 mM asparagine. Otherwise asparagine could not elicit rhythmicity in darkness or in dim continuous light (< 5 [i'W m-).

Jerebzoff -Ouintin, S. and Jerebzoff, S. 1985. L-Asparaginase activity in Leptospkaeria michotii. Isolation and properties of two forms of the enzyme, -Physiol, Plant, 64: 74-80.The properties of L-asparaginase (EC 3.5.1.1) in Leptosphaeria michotii (West) Sacc, which has previously been shown to have an activity rhythm, were analyzed. Two forms of L-asparaginase were isolated from acetic acid and ammonium sulfate fractionations followed by DEAE-Sephacel chromatography. The activity of L-asparaginase changed rhythmically with the same period as that of crude extracts, but the rhythms of the two enzyme forms were out of phase. The two asparaginase forms differed in their isoelectric points and the substrate concentrations for attaining halfmaximal velocity; non-Michaelis-Menten kinetics for hydrolysis of L-asparagine were observed. Analyses of asparaginase form II by polyacrylamide gel eiectrophoresis showed that four proteins, irrespective of the phase of the activity rhythm at which the enzyme was extracted, could be detected: asparaginase oligomer (M, I300O0 to 140000), its dimer, an aggregate (M, 500000 to 600000) having a low asparaginase activity, and a protein (M^ 60000) without asparaginase activity; the same proteins were found in asparaginase form 1. These results indicate that L. michotii asparaginase could be implicated in a protein complex.Additional key words -Asparagine, fungus, rhythmic enzyme activity, oscillating system. 5*. Jerebioff-Quintin and S. Jerebzoff (reprint requests). Lab.