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EFFECT OF PHOSPHOLIPASES A AND C ON FREE AMINO ACID CONTENT OF THE SQUID AXON 1
Author(s) -
Rosenberg P.,
Khairallah E. A.
Publication year - 1974
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1974.tb06915.x
Subject(s) - axoplasm , phospholipase , phospholipase a2 , phospholipid , membrane , biochemistry , chemistry , axon , squid , squid giant axon , biophysics , amino acid , phospholipase c , incubation , enzyme , biology , anatomy , ecology
— Squid axonal preparations consisting of the giant axon plus adhering small nerve fibres were incubated for 30 min with phospholipase A (1, 0.2 and 0.025 mg/ml); phospholipase C (10 and 0.5 mg/ml) or lysolecithin (1 and 0.2 mg/ml) followed by another 30 min incubation in normal sea water. The axoplasm and envelope (sheath) of the axonal preparation were then separated and the phospholipids and free amino acids determined. The released amino acids were also measured in the incubation solutions. Compared to phospholipase C, phospholipase A caused a much greater reduction in the free amino acid content of axoplasm and envelope; and a concomitant much greater increase in amino acids released into the incubation solutions, even when phospholipase A was used in concentrations which caused less phospholipid splitting than phospholipase C. Lysolecithin had a much weaker effect than phospholipase A. It is concluded that disruption of hydrophobic binding has a much greater effect on the structure of the non‐lipid portion of the axonal membranes than does disruption of hydrophilic (electrostatic) forces of interaction. Our results can be interpreted in terms of the protein‐crystal or mosaic models of membrane structure whereas they do not support the unit membrane hypothesis.