Catalase Degradation in Sunflower Cotyledons during Peroxisome Transition from Glyoxysomal to Leaf Peroxisomal Function

Self Cite

Based on measurements of total catalase hematin and the degradation constants of catalase hematin, zero order rate constants for the synthesis of catalase were determined during the development of sunflower cotyledons (Hellanthus annuus L.).Catalase synthesis reached a sharp maximum of about 400 picomoles hematin per day per cotyledon at day 1.5 during the elaboration of glyoxysomes in the dark. During the transition of glyoxysomes to leaf peroxisomes (greening cotyledons, day 2.5 to 5) catalase synthesis was constant at a level of about 30 to 40 picomoles hematin per day per cotyledon. In the cotyledons of seedlings kept in the dark (day 2.5 to 5) catalase synthesis did not exceed 10 picomoles hematin per day per cotyledon. During the peroxisome transition in the light, total catalase hematin was maintained at a high level, whereas total catalase activity rapidly decreased. In continuous darkness, total catalase hematin decreased considerably from a peak at day 2. The results show that both catalase synthesis and catalase degradation are regulated by light. The tumover characteristics of catalase are in accordance with the concept that glyoxysomes are transformed to leaf peroxisomes as described by the one population model and contradict the two population model and the enzyme synthesis changeover model which both postulate de novo formation of the leaf peroxisome population and degradation of the glyoxysome population.Studies on the transition of peroxisomes from glyoxysomal to leafperoxisomal function in greening oil storing cotyledons have given rise to three models (1). The two population model (6, 7) and the "enzyme synthesis changeover" model (14, 15) postulate a breakdown of glyoxysomes and a de novo formation of leaf peroxisomes, whereas the one population model (18) assumes that glyoxysomes are transformed into leaf peroxisomes. In contrast to the two population model, both the enzyme synthesis changeover model and the one population model predict peroxisomes of intermediary character, i.e. organelles containing both glyoxysomal and leaf peroxisomal enzymes during the transition stage. According to the enzyme synthesis changeover model, leaf-type peroxisomes are formed as a consequence of a turnover of the whole organelles, whereas in the one population model individual enzyme turnover within the same organelle leads to a gradual replacement of glyoxysomal by leaf peroxisomal enzymes. ' Supported by grants from the Deutsche Forschungsgemeinschaft and the Gesellschaft zur Forderung der Westfilischen WilhelmsUniversitat.The existence of peroxisomes of intermediary character has been demonstrated recently in immunocytochemical studies (10, 1 1, 17). These results provide strong evidence against the two population model which postulates two independent populations of peroxisomes functioning exclusively as either glyoxysomes or leaf peroxisomes. The question, however, whether individual enzyme turnover or organelle turnover accounts for the formation of the intermediary peroxisomes, could not be de...

Section: Discussionsupporting

confidence: 70%

Section: Time Course Of Catalase Activity and Catalase Hematinmentioning

confidence: 99%

See 1 more Smart Citation

Catalase Synthesis and Turnover during Peroxisome Transition in the Cotyledons of Helianthus annuus L.

Eising

Gerhardt²

1989

Self Cite

“…Refs. 4,6, and this paper) the mechanism of regulation has not been determined but could be the result of changes in rates of synthesis, degradation, or by covalent modification of the protein. The determination by Eising et al (3) that the sharp decline in catalase activity in greening sunflower cotyledons was due to the formation of an inactive but largely intact protein molecule may be pertinent to studies of environmentally related changes in catalase activity.…”

mentioning

confidence: 99%

Regulation of Catalase Activity in Leaves of Nicotiana sylvestris by High CO₂

Havir¹,

McHale²

1989

The effect of high CO2 (1% C02/21% 02) on the activity of specific forms of catalase (CAT-1, -2, and -3) (EA Havir, NA McHale [1987] Plant Physiol 84: 450-455) in seedling leaves of tobacco (Nicotiana sylvestris, Nicotiana tabacum) was examined. In high C02, total catalase activity decreased by 50% in the first 2 days, followed by a more gradual decline in the next 4 days. The loss of total activity resulted primarily from a decrease in CAT-1 catalase. In contrast, the activity of CAT-3 catalase, a form with enhanced peroxidatic activity, increased 3-fold in high CO2 relative to aiontrols after 4 days. Short-term exposure to high CO2 indicated that the 50% loss of total activity occurs in the first 12 hours. Catalase levels increased to normal within 12 hours after seedlings were retumed to air. When seedlings were transferred to air after prolonged exposure to high CO2 (13 days), the levels of CAT-1 catalase were partially restored while CAT-3 remained at its elevated level. Levels of superoxide dismutase activity and those of several peroxisomal enzymes were not affected by high CO2. Total catalase levels did not decline when seedlings were exposed to atmospheres of 0.04% C02/5% 02 or 0.04% C02/1% 02, indicating that regulation of catalase in high CO2 is not related directly to suppression of photorespiration. Antibodies prepared against CAT-1 catalase from N. tabacum reacted strongly against CAT-1 catalase from both N. sylvestris and N. tabacum but not against CAT-3 catalase from either species. This observation, along with the rapid changes in CAT-I and the much slower changes in CAT-3 suggest that one form is not directly derived from the other. concentration (5, 19) have been shown to influence catalase activity in mature plants. For example, Fair et al. (5) demonstrated that catalase activity was suppressed when barley was grown in 1 to 5% CO2 and in 2% 02. Other peroxisomal enzymes were suppressed also and thus the effect in barley may be generally on peroxisomal turnover. In cases where catalase regulation is independent of peroxisomal turnover (e.g. Refs. 4, 6, and this paper) the mechanism of regulation has not been determined but could be the result of changes in rates of synthesis, degradation, or by covalent modification of the protein. The determination by Eising et al. (3) that the sharp decline in catalase activity in greening sunflower cotyledons was due to the formation of an inactive but largely intact protein molecule may be pertinent to studies of environmentally related changes in catalase activity.We previously showed that catalase activity in leaves of tobacco seedlings was distributed among several forms, one ofwhich had enhanced peroxidatic activity and that there was a change in distribution with time of development (l1). Furthermore, transfer of the seedlings to 1% C02/2 1% 02 for 4 d reduced total catalase activity by about 50% and altered the distribution ofthe activities. Here we show that the decline in catalase in high CO2 is very rapid and results primarily from the los...

“…Results obtained from a few studies indicate that the general mechanism is one of individual protein degradation rather than a degradation of the whole organelles (1, 8,9,11,12,22,27,28). The concept of individual protein degradation suggests that (at least) initiating steps of the degradative pathway are localized in the peroxisomes.…”

mentioning

confidence: 99%

Turnover of Catalase Heme and Apoprotein Moieties in Cotyledons of Sunflower Seedlings

Eising¹,

Süselbeck²

1991

Self Cite

The turnover of catalase apoprotein and catalase heme was studied in cotyledons of sunflower (Helianthus annuus L.) seedlings by density labeling of apoprotein and radioactive labeling of heme moieties. The heavy isotope (50% 2H20) and the radioactive isotope ([14C]5-aminolevulinic acid) were applied either during growth in the dark (day 0-2.5) or in the light (day 2.5 and 5). Following isopycnic centrifugation of catalase purified from cotyledons of 5-day-old seedlings, superimposition curve fitting was used to determine the amounts of radioactive heme moieties in native and density-labeled catalase. Data from these determinations indicated that turnover of catalase heme and apoprotein essentially was coordinate. Only small amounts of heme groups were recycled into newly synthesized apoprotein during growth in the light, and no evidence was found for an exchange of heme groups in apoprotein moieties. It followed from these observations that degradation of catalase apoprotein was slightly faster than that of catalase heme. A degradation constant for catalase apoprotein of 0.263 per day was determined from the data on heme recycling and the degradation constant of catalase heme determined previously to be 0.205 per day (R Eising, B Gerhardt [1987] Plant Physiol 84: 225-232).In comparison with the increment of our knowledge on the biogenesis of peroxisomal proteins in plants in the last several years, only little progress was made in understanding the turnover (degradation) of proteins from plant peroxisomes. Results obtained from a few studies indicate that the general mechanism is one of individual protein degradation rather than a degradation of the whole organelles (1,8,9,11,12,22,27,28). The concept of individual protein degradation suggests that (at least) initiating steps of the degradative pathway are localized in the peroxisomes. These steps are not necessarily proteolytic processes, but could be any chemical modification (e.g. oxidation, dephosphorylation), or a specific export of proteins destined for degradation in other cell compartments.