Biochemistry Of The Eye

BUTTERWORTH-HEINEMANN An Imprint of Elsevier Science The Curtis Center Independence Square West Philadelphia, Pennsylvania 19106-3399 Copyright © 2003, 1994 Elsevier Inc. All Rights Reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writting from the publisher. Library of Congress Cataloging-in-Publication Data Whikehart, David R. Biochemistry of the eye/David R. Whikehart.–2nd ed. p. ; cm. Includes bibliographical references and index. ISBN 0-7506-7152-1 1. Eye–Metabolism. 2. Eye–Physiology. I. Title. [DNLM: 1. Eye–chemistry. 2. Eye–physiopathology. WW 101 W561b 2003] QP475 .W48 2003 612.8′4–dc21 2002026298 Publishing Director: Linda Duncan Managing Editor: Christie M. Hart Project Manager: Mary B. Stermel Printed in USA Last digit is the print number: 9 8 7 6 5 4 3 2 1 Preface to the 2nd edition It is a modest statement to say that much has happened in this area since the 1st edition appeared. A perusal through the literature will show that great strides have occurred in the understanding of many heretofore difficult sections of ocular biochemistry including: diabetes, visual transduction, chemical tissue degradation, immunochemistry, cataractogenesis, and so on. This new edition continues the tradition of the former edition in perusing the basic parts of biochemistry first and then continuing on to describe those characteristics of biochemistry that are peculiar and characteristic to the eye. It is my philosophy that illustrations are of immense help in understanding difficult concepts and I have liberally included them throughout the book. Two new chapters on aqueous/ocular fluids and tissue degradation have been added. In the older chapters much updating and revision should be evident to those familiar with the first edition. As always, the objective in putting together such a work is to increase the student’s and reader’s awareness of those biochemical structures and molecular events that influence the normal and pathological performance of the eye as an organ of vision. The complexity of all that is involved in vision and vision care can hardly be understood without some knowledge of the molecular events that go on in the eye. David R. Whikehart v Acknowledgments I am indebted to those students who have made suggestions about improving the book prior to publication. Gratitude is also expressed to my daughter, Erin Whikehart, who designed the cover, and to Brigette Bailey, who allowed me to photograph her eye for the cover. Finally, I am especially thankful to Christie Hart, the managing editor of Elsevier Science (Butterworth-Heinemann Division) and to Karen Oberheim, formerly of Butterworth-Heinemann, for their long standing patience as I wrote this text. vii Color Plate 1 One of several proposed structures for α-crystallin. ➤ The model shows bound rings of crystallin subunits laid on top of each other. The large subunit spheres are hydrophilic C-terminal domains while the small subunit spheres are hydrophobic N-terminal domains. Extending from the C-terminal domains are C-terminal peptide extensions that cover the central cavity where chaperone activity may take place. (Redrawn from Carver JA, Aquilina JA, and Truscott RJW: A possible chaperone-like quaternary structure for a-crystallin. Exp Eye Res 59: 231–234, 1994.) C cytosol disc membrane Phe/Tyr (7 nm) 312 129 Ser/Ala (18 nm) N Ala/Thr (14 nm) Ala/Ser (3 nm) Tyr/His (28 nm) extracellular space 129 Glu #129, the site of attachment for the Schiff base counterion 312 Lys #312, the site of covalent attachm