Benders'dictionary of nutrition and food technology

144cytochromes haem-containing proteins. Some react with oxygendirectly; others are intermediates in the oxidation of reducedcoenzymes. Unlike haemoglobin, the iron in the haem ofcytochromes undergoes oxidation and reduction.cytochromes P450 A family of cytochromes involved in thedetoxication system of the body (see phase i metabolism). Theyact on a wide variety of (potentially toxic) compounds, bothendogenous metabolites and foreign compounds (xenobiotics),rendering them more water-soluble, and more readily conjugatedfor excretion in the urine.The CYP26 group of cytochromes P450 are specific forretinoic acid, leading to a variety of metabolites that may bephysiologically active (especially in cell differentiation), including4-hydroxy-, 4-oxo-, 5,6-epoxy- and 18-hydroxy-retinoic acid.cytokines A number of proteins secreted by cells in response tovarious stimuli that act to regulate proliferation and differentiation,immune and inflammatory responses, etc.Cytokines produced by lymphocytes are sometimes known aslymphokines; those from monocytes as monokines; thosesecreted by adipose tissue as adipokines or adipocytokines.cytokinins Plant hormones derived from isopentenyl adenosine;produced by root tips, seed embryos, developing fruits and buds;they stimulate cell division (cytokinesis) and regulate developmentof the plant.See also auxins.cytosine One of the pyrimidine bases of nucleic acids.DD-, L- and DL- Prefixes to chemical names for compounds thathave a centre of asymmetry in the molecule, and which cantherefore have two forms.Most naturally occurring sugars have the d-conformation;apart from a few microbial proteins and some invertebratepeptides, all the naturally occurring amino acids have the l-configuration. Chemical synthesis yields a mixture of the d- andl-isomers (the racemic mixture), generally shown as dl-.See also isomers; optical activity; R- and S-.d- and l- An obsolete way of indicating dextrorotatoryand laevorotatory optical activity, now replaced by (+) and(−).dabberlocks Edible seaweed, Alaria esculenta.dadhi See milk, fermented.dagé Indonesian; fermented presscake from various oilseeds orlegumes or starch crops, soaked in water and left to undergo