Enr J Biochem. 185,485-486 (1989) C FbBS 1989 - EJB 89 0804

IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN)

Nomenclature of glycoproteins, glycopeptides and peptidoglycans Correction to Recommendations 1985

The following correction should be made to the document published in Eur. J. Bioclzenz. 159, 1 -6 (1986): Page 2, column 2, section 2.3, lines 2/3: ,for muramic acid (2-amino-3-O-[(S)-l -carboxyethyl]-2-deoxy-~-glucose), w a d

muramk acid ~2-amino-3-O-[(R)-l-carboxyethyl]-2-deoxy-~-glucose).

Nomenclature Committee of the International Union of Biochemistry (NC-IUB)

Nomenclature for multienzymes Recommendations 1989

NC-IUB approves the following definitions to assist in reporting and discussing multienzymes.

DEFINITIONS Multienzyme. A protein possessing more than one catalytic

function contributed by distinct parts of a polypeptide chain (‘doniains’), or by distinct subunits, or both.

Mullierzzyt?ze cotnplex. A multienzyme with catalytic do- mains on more than one type of polypeptide chain.

Multienzyme polypeptide. A polypcptide chain containing at least two typcs of catalytic domains.

Catalytic. dumain. Any part of a polypeptide chain that possesses a catalytic function. It may contain more than one structural domain.

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called ‘autonomous’.

ponents of multienzymc complexes.

1. Catalytic functions due to distinct domains may be

2. Multienzyme polypeptides may themselves be com-

This is a document of the Nomenclature Committee or the Inter- national Union of Biochemistry (NC-IIJB), whose menbers are J. F. G. Vliegenthart (Chairman), C. R. Cantor, M. A. Chester, C. Liebecq (representing ihc IUB Committee of Editors of Biochemical Journals), G. P. Moss. W. Saenger. N. Sharon and P. Venetianer. NC-lUB thanks a panel whose members were J. R. Coggins (UK, convenor), H. von Dohrcn (FRG), P. Friedrich (Hungary), R. N. Perham (UK), P. A. Srcre (USA) and C . R. Welch (USA), Tor drafting thesc rec- ommendations, as well as former mcmbcrs of NC-IUB and present and former members of the IUPAC-IUB Joint Commission on Bio- chemical Nomcnciature (JCBN). namely J. R . Bull, A. J. Cornish- Bowden, H. B. F. Dixon, P. Karlson, J. Reedijk, E. J. Van Lenten and E. C. Wcbb. for help in drafting thcm. Comments may be sent to any member oTNC-IUB or to its secretary. M. A. Chester. BioCarb AB, Fack. S-223 70 Lund, Sweden.

3. The definitions may be illustrated by giving criteria that may be used to designate a given system as multienzyme polypeptide:

a) They exclude single enzymes that can catalyse different reactions using the same catalytic centre.

b) They exclude regulatory ligand-binding domains, as the definition demands multiple catalytic functions.

c) Two or more catalytic domains must be demonstrated on a single polypeptide chain: this implies distinct domains for the different catalytic functions. Methods used for this include active-site labelling. followed by peptide mapping or gel electrophoresis in the presence of sodium dodecyl sulfate, and limited proteolysis (as most known multienzymc polypcp- tides contain domains joincd by peptidase-sensitive linker re- gions).

d) Genetic methods should also be used to demonstrate that a single gene encodes several autonomous functional protein domains.

SYMBOLISM There may be contexts where symbols arc required to

indicate the nature of domains and the types and strengths of interactions between them. For these, the following system, which is modified from that of von Dohren [I], may be used. I t should be used with caution and with a clear statement of the structural meaning intended, because there may not be clear dividing lines between the degrees of strength of associa- tion between protein subunits.

Catalytic domains are given uppcr-case letters from early in the alphabet, A; B, C, ...; substrate-carrier domains are given upper-case letters from late in the alphabet, P, Q, R, . . .; regulatory domains are given lower-case letters from carly in the alphabet, a, b, c, ...; domains of unknown function may be given lower-case letters from late in the alphabet, x, y, z, . . . Domains in the same polypeptide chain are placed within the same pair of parentheses, so that (ABC) represents

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a multicnzyme polypeptide, whereas (A)(B)(C) represents a multienzyme complex. If these letters are assigned to particu- lar functions, then (ABC) indicates that A, B and C occur in the sequence in that order, whereas (A, B, C) is used when the order is not known.

Thus inammaliaii aldolase would be symbolyzed as (A)4r tryptophan synthase from Escherichia coli as (A)2(B)2, and the arom multienzyme I polypeptide of Neurospora crassa as (ABCDE)z.

i.e.enzymesEC4.6.1.3.T:C4.2.1.10,EC1.1.1.25,EC2.7.1.71 and EC 2.5.1.19.

Brackets of the type (> may be used to indicate stable association, so that portraying (A)2(B)2 as ((A),(B),) indi- cates that the association is stable, whereas portraying it as {(A)(B)}z indicates that each A chain binds one B Chain tightly but that the two {(A)(B)} units are more loosely associ- ated.

REFERENCE 1. von Dohren, H. (1980) Trends Biochern. Sci. 5(3), VIII