Oxygen-transporting proteins

Table 4.1 Some Properties of Oxygen Transport Proteins...

The simplest way to pack a pair of adjacent helices is to place them anti-parallel to one another connected by a short loop. A frequently encountered domain structure in proteins is a bundle of four helices with their long axes aligned around a central-hydrophobic core. This is illustrated by myohaemerythrin (Figure 4.11), a non-haem oxygen transport protein in marine worms. 

Catechol oxidase and tyrosinase are among the enzymes that have Type 3 dinuclear centres. However, the prototype of this class of proteins is the invertebrate oxygen transport protein, haemocyanin (Figure 14.5), for which structures of the oxy and deoxy forms have been determined at high resolution and confirm, as predicted from model compounds, that the... 

It may come as a surprise that CO is synthesized by the human body and has roles in human metabolism. Specifically, an enzyme that degrades heme, a constituent of hemoglobin, our oxygen-transporting protein, makes CO, which is a neurotransmitter. Much more about neurotransmitters follows in chapter 21 when we talk about the central nervous system. For the present, just understand that specialized cells known as neurons are the conduits for communication in the nervous system. Neurotransmitters are small molecules that relay information from one neuron to another. Neurotransmitter CO is made, functions, and is quickly destroyed. Personally, I find it surprising that CO has such a critical role in the nervous system. Surprised or not, there it is and there is no doubt about it. 

FIGURE 3-1 Some functions of proteins, (a) The light produced by fireflies is the result of a reaction involving the protein luciferin and ATP, catalyzed by the enzyme luciferase (see Box 13-2). (b) Erythrocytes contain large amounts of the oxygen-transporting protein hemoglobin. (c) The protein keratin, formed by all vertebrates, is the chief structural component of hair, scales, horn, wool, nails, and feath-... 

In the following sections, examples of all the classes of reaction given above will be discussed, with emphasis on those that have been well studied. Many of the enzymes involved in these processes are hemoproteins, but non-heme prosthetic groups are important in oxygenases and are also present in some oxidases. Copper is an important metal in this context, and is present in the oxygen transport protein hemocyanin, and in oxidases such as cytochrome oxidase and laccase. Some flavoenzymes are important too, but will not be covered in this discussion. 

Transport proteins Transport oxygen and other substances through the body Hemoglobin tion of Oxygen Transport Proteins, "J. Chem. Educ., Vol. 64,1987,... 

Hemocyanins (He) are oxygen-transport proteins found in the blood of insects, Crustacea and other invertebrates (MW 105-107) (20). One of the smallest He (MW 450,000) extracted from spiny lobster consists of six subunits, each containing two Cu atoms. Upon oxygenation, the deoxy-form (Cu(I), colorless) turns to blue (Cu(II), blue blood ) by binding one molecule of O2 per two Cu atoms. Freedman et al. (21) measured the RR spectra of oxy-Hc extracted from Crustacea and observed the v(02) near 750 cm-1, which shifts to 705 cm-1 upon 1602/1802 substitution. In contrast to oxy-Hr, the two O atoms of the coordinated O2 were found to be equivalent since... 

Occurrence of hemocyanin related proteins in organisms. While textbooks teU that Hes occm only in arthropods and molluscs, recently Hes were also found in other phyla. The velvet worms (Onychophora) are considered living fossils and are closely related to the Euarthropoda. Onychophora possess a tracheal system for respiratory function, thus oxygen transport proteins have been considered unnecessary. In the hemolymph of the Epiperipatus sp. (Onychophora Peripatidae), an arthropod-type hemocyanin was found, demonstrating that such proteins exist outside the Euarthropoda. ... 

Brunori, M., Giardina, B., Bannister, J. V. Oxygen-transport proteins, in Inorganic... 

To begin, we will consider the principles of allostery by examining two proteins the enzyme aspartate transcarhamoylase and the oxygen-transporting protein hemoglobin. 

We will consider two specific examples of allosteric proteins—one an enzyme and the other an oxygen transport protein. 

Volbeda, A. and Hoi, W. G. J. (1989). Pseudo 2-fold symmetry in the copper-binding domain of arthropodan haemocyanins possible implications for the evolution of oxygen transport proteins. Journal of Molecular Biology, 206, 531 6. 

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