Factor IX

Factor IX (or Christmas factor) (EC 3.4.21.22) is one of the serine proteases of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes hemophilia B. It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to hemophilia.

It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.

Physiology

Factor IX is produced as a zymogen, an inactive precursor. It is processed to remove the signal peptide, glycosylated and then cleaved by factor XIa (of the contact pathway) or factor VIIa (of the tissue factor pathway) to produce a two-chain form where the chains are linked by a disulfide bridge. When activated into factor IXa, in the presence of Ca²⁺, membrane phospholipids, and a Factor VIII cofactor, it hydrolyses one arginine-isoleucine bond in factor X to form factor Xa.

Factor IX is inhibited by antithrombin.

Factor IX expression increases with age in humans and mice. In mouse models mutations within the promoter region of factor IX have an age-dependent phenotype.

Factor

Factor, a Latin word meaning "who/which acts", may refer to:

Commerce

Science and technology

Biology

Computer science and information technology

Factor (programming language)

Factor is a stack-oriented programming language created by Slava Pestov. Factor is dynamically typed and has automatic memory management, as well as powerful metaprogramming features. The language has a single implementation featuring a self-hosted optimizing compiler and an interactive development environment. The Factor distribution includes a large standard library.

History

Slava Pestov created Factor in 2003 as a scripting language for a video game. The initial implementation, now referred to as JFactor, was implemented in Java and ran on the Java Virtual Machine. Though the early language resembled modern Factor superficially in terms of syntax, the modern language is very different in practical terms and the current implementation is much faster.

The language has changed significantly over time. Originally, Factor programs centered on manipulating Java objects with Java's reflection capabilities. From the beginning, the design philosophy has been to modify the language to suit programs written in it. As the Factor implementation and standard libraries grew more detailed, the need for certain language features became clear, and they were added. JFactor did not have an object system where you could define your own classes, and early versions of native Factor were the same; the language was similar to Scheme in this way. Today, the object system is a central part of Factor. Other important language features such as tuple classes, combinator inlining, macros, user-defined parsing words and the modern vocabulary system were only added in a piecemeal fashion as their utility became clear.

Factoring (finance)

Factoring is a financial transaction and a type of debtor finance in which a business sells its accounts receivable (i.e., invoices) to a third party (called a factor) at a discount. A business will sometimes factor its receivable assets to meet its present and immediate cash needs.Forfaiting is a factoring arrangement used in international trade finance by exporters who wish to sell their receivables to a forfaiter. Factoring is commonly referred to as accounts receivable factoring, invoice factoring, and sometimes accounts receivable financing. Accounts receivable financing is a term more accurately used to describe a form of asset based lending against accounts receivable.

Factoring is not the same as invoice discounting (which is called an "Assignment of Accounts Receivable" in American accounting – as propagated by FASB within GAAP). Factoring is the sale of receivables, whereas invoice discounting ("assignment of accounts receivable" in American accounting) is a borrowing that involves the use of the accounts receivable assets as collateral for the loan. However, in some other markets, such as the UK, invoice discounting is considered to be a form of factoring, involving the "assignment of receivables", that is included in official factoring statistics. It is therefore also not considered to be borrowing in the UK. In the UK the arrangement is usually confidential in that the debtor is not notified of the assignment of the receivable and the seller of the receivable collects the debt on behalf of the factor. In the UK, the main difference between factoring and invoice discounting is confidentiality.