Differences in the protocollagen hydroxylase activities from Ascaris muscle and hypodermis
| Autor: | Milos Chvapil, Eva Ehrlich, Mark M. Boucek |
|---|---|
| Rok vydání: | 1970 |
| Předmět: |
Cuticle
Biophysics chemistry.chemical_element Protocollagen hydroxylase Biochemistry Oxygen Michaelis–Menten kinetics Mixed Function Oxygenases Animals Molecular Biology chemistry.chemical_classification Carbon Isotopes biology Ascaris Lysine Muscles Protocollagen Substrate (chemistry) biology.organism_classification Molecular biology Kinetics Enzyme chemistry Ketoglutaric Acids Collagen |
| Zdroj: | Archives of Biochemistry and Biophysics. 140:11-18 |
| ISSN: | 0003-9861 |
| DOI: | 10.1016/0003-9861(70)90003-2 |
| Popis: | Protocollagen hydroxylase (PCH) was partially purified from Ascaris lumbricoides muscle and from cuticle fluid. This fluid is found in the space formed between the cuticle and muscle layer when the worms are frozen at −40 ° for several days and then thawed. The enzyme in this fluid is probably derived from the hypodermal cells of the subcuticular layer which are disrupted during shrinkage. While PCH is present in the muscle layer and in the fluid, no PCH activity has been found in cleaned cuticle. Muscle PCH is optimally active at 1–5% O 2 . High oxygen concentrations (30%) reversibly inhibit the enzyme. Cuticle fluid PCH does not show maximal activity until 20% O 2 and remains elevated to at least 40% O 2 . The Michaelis constant ( K m ) for oxygen substrate was 1.11% O 2 for muscle PCH and 2.87% O 2 for PCH isolated from fluid. The protocollagen substrate K m for muscle PCH at 5% O 2 was 1.25 mg substrate protein/ml; for the cuticle fluid, 5.52. At 30% O 2 these values were 0.78 and 12.9, respectively. With respect to α-ketoglutarate, the K m for muscle PCH at 5% O 2 was 1.6 × 10 −4 m ; for cuticle fluid, 8 × 10 −3 m . 14 C-Lys-protocollagen substrate was hydroxylated by both the fluid and muscle crude enzyme extract at 5%, or 30% oxygen. Here again, muscle PCH became less active at higher O 2 concentrations. The evidence indicates two different PCH activities, one in the muscle and one in the hypodermis. It is not yet known whether these two activities are due to two distinct enzymes or to the effects of the two microenvironments. |
| Databáze: | OpenAIRE |
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